diff --git a/src/builtins/argparse.rs b/src/builtins/argparse.rs
index 936f19ee7..7101d4728 100644
--- a/src/builtins/argparse.rs
+++ b/src/builtins/argparse.rs
@@ -738,8 +738,7 @@ fn validate_arg<'opts>(
     );
 
     for output in cmd_output {
-        streams.err.append(&output);
-        streams.err.append_char('\n');
+        streams.err.appendln(&output);
     }
     parser.vars().pop(parser.is_repainting());
     retval.map(|()| SUCCESS)
diff --git a/src/builtins/commandline.rs b/src/builtins/commandline.rs
index 9ecbe6385..ab02b14c0 100644
--- a/src/builtins/commandline.rs
+++ b/src/builtins/commandline.rs
@@ -156,11 +156,12 @@ fn write_part(
 
     let Some(token_mode) = token_mode else {
         if cut_at_cursor {
-            streams.out.append(&buffer[range.start..range.start + pos]);
+            streams
+                .out
+                .appendln(&buffer[range.start..range.start + pos]);
         } else {
-            streams.out.append(&buffer[range]);
+            streams.out.appendln(&buffer[range]);
         }
-        streams.out.append_char('\n');
         return;
     };
 
diff --git a/src/builtins/complete.rs b/src/builtins/complete.rs
index 3343fb459..98564f9f9 100644
--- a/src/builtins/complete.rs
+++ b/src/builtins/complete.rs
@@ -452,13 +452,12 @@ pub fn complete(parser: &Parser, streams: &mut IoStreams, argv: &mut [&wstr]) ->
         if detect_parse_errors(condition_string, Some(&mut errors), false).is_err() {
             for error in errors {
                 let prefix = cmd.to_owned() + L!(": -n '") + &condition_string[..] + L!("': ");
-                streams.err.append(&error.describe_with_prefix(
+                streams.err.appendln(&error.describe_with_prefix(
                     condition_string,
                     &prefix,
                     parser.is_interactive(),
                     false,
                 ));
-                streams.err.append_char('\n');
             }
             return Err(STATUS_CMD_ERROR);
         }
@@ -475,8 +474,7 @@ pub fn complete(parser: &Parser, streams: &mut IoStreams, argv: &mut [&wstr]) ->
                 cmd,
                 comp
             ));
-            streams.err.append(&err_text);
-            streams.err.append_char('\n');
+            streams.err.appendln(&err_text);
             return Err(STATUS_CMD_ERROR);
         }
     }
diff --git a/src/builtins/printf.rs b/src/builtins/printf.rs
index 2bb06e08e..196073a4f 100644
--- a/src/builtins/printf.rs
+++ b/src/builtins/printf.rs
@@ -578,7 +578,7 @@ fn nonfatal_error<Str: AsRef<wstr>>(&mut self, errstr: Str) {
 
         self.streams.err.append(errstr);
         if !errstr.ends_with('\n') {
-            self.streams.err.append_char('\n');
+            self.streams.err.append('\n');
         }
 
         // We set the exit code to error, because one occurred,
@@ -602,7 +602,7 @@ fn fatal_error<Str: AsRef<wstr>>(&mut self, errstr: Str) {
 
         self.streams.err.append(errstr);
         if !errstr.ends_with('\n') {
-            self.streams.err.append_char('\n');
+            self.streams.err.append('\n');
         }
 
         self.exit_code = Err(STATUS_CMD_ERROR);
diff --git a/src/builtins/set.rs b/src/builtins/set.rs
index 3fd563651..6e4b4a8ec 100644
--- a/src/builtins/set.rs
+++ b/src/builtins/set.rs
@@ -677,19 +677,20 @@ fn show_scope(var_name: &wstr, scope: EnvMode, streams: &mut IoStreams, vars: &d
     if EnvVar::flags_for(var_name).contains(EnvVarFlags::READ_ONLY) {
         streams.out.append(wgettext!(" (read-only)\n"));
     } else {
-        streams.out.append_char('\n');
+        streams.out.append('\n');
     }
 
     for i in 0..vals.len() {
         if vals.len() > 100 {
             if i == 50 {
                 // try to print a mid-line ellipsis because we are eliding lines not words
-                streams.out.append(if u32::from(get_ellipsis_char()) > 256 {
-                    L!("\u{22EF}")
-                } else {
-                    get_ellipsis_str()
-                });
-                streams.out.append_char('\n');
+                streams
+                    .out
+                    .appendln(if u32::from(get_ellipsis_char()) > 256 {
+                        L!("\u{22EF}")
+                    } else {
+                        get_ellipsis_str()
+                    });
             }
             if i >= 50 && i < vals.len() - 50 {
                 continue;
diff --git a/src/builtins/shared.rs b/src/builtins/shared.rs
index b1eefe5d1..42f7ef059 100644
--- a/src/builtins/shared.rs
+++ b/src/builtins/shared.rs
@@ -696,12 +696,11 @@ pub fn builtin_unexpected_argument(
 
 /// Print the backtrace and call for help that we use at the end of error messages.
 pub fn builtin_print_error_trailer(parser: &Parser, b: &mut OutputStream, cmd: &wstr) {
-    b.append_char('\n');
+    b.append('\n');
     let stacktrace = parser.current_line();
     // Don't print two empty lines if we don't have a stacktrace.
     if !stacktrace.is_empty() {
-        b.append(&stacktrace);
-        b.append_char('\n');
+        b.appendln(&stacktrace);
     }
     b.append(&wgettext_fmt!(
         "(Type 'help %s' for related documentation)\n",
@@ -717,8 +716,7 @@ pub fn builtin_wperror(program_name: &wstr, streams: &mut IoStreams) {
     streams.err.append(L!(": "));
     if err.0 != 0 {
         let werr = str2wcstring(err.to_string());
-        streams.err.append(&werr);
-        streams.err.append_char('\n');
+        streams.err.appendln(&werr);
     }
 }
 
diff --git a/src/builtins/status.rs b/src/builtins/status.rs
index 973775785..9aac40258 100644
--- a/src/builtins/status.rs
+++ b/src/builtins/status.rs
@@ -728,8 +728,7 @@ pub fn status(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> B
                 }
                 STATUS_CURRENT_COMMANDLINE => {
                     let commandline = &parser.libdata().status_vars.commandline;
-                    streams.out.append(commandline);
-                    streams.out.append_char('\n');
+                    streams.out.appendln(commandline);
                 }
                 STATUS_FISH_PATH => {
                     use crate::env::config_paths::FishPath::*;
diff --git a/src/builtins/string/join.rs b/src/builtins/string/join.rs
index c5576690a..e1d69d43f 100644
--- a/src/builtins/string/join.rs
+++ b/src/builtins/string/join.rs
@@ -84,9 +84,9 @@ fn handle(
 
         if nargs > 0 && !self.quiet {
             if self.is_join0 {
-                streams.out.append_char('\0');
+                streams.out.append('\0');
             } else if print_trailing_newline {
-                streams.out.append_char('\n');
+                streams.out.append('\n');
             }
         }
 
diff --git a/src/builtins/string/repeat.rs b/src/builtins/string/repeat.rs
index 7473c1aab..3db3f0cd4 100644
--- a/src/builtins/string/repeat.rs
+++ b/src/builtins/string/repeat.rs
@@ -102,7 +102,7 @@ fn handle(
             }
 
             if !first {
-                streams.out.append_char('\n');
+                streams.out.append('\n');
             }
             first = false;
 
@@ -165,7 +165,7 @@ fn handle(
 
         // Historical behavior is to never append a newline if all strings were empty.
         if !self.quiet && !self.no_newline && !all_empty && print_trailing_newline {
-            streams.out.append_char('\n');
+            streams.out.append('\n');
         }
 
         if all_empty {
diff --git a/src/builtins/string/replace.rs b/src/builtins/string/replace.rs
index de643ed42..866f01c01 100644
--- a/src/builtins/string/replace.rs
+++ b/src/builtins/string/replace.rs
@@ -116,7 +116,7 @@ fn handle(
             if !self.quiet && (!self.filter || replaced) {
                 streams.out.append(&result);
                 if want_newline {
-                    streams.out.append_char('\n');
+                    streams.out.append('\n');
                 }
             }
 
diff --git a/src/builtins/string/sub.rs b/src/builtins/string/sub.rs
index e015ffb6e..4f9c29901 100644
--- a/src/builtins/string/sub.rs
+++ b/src/builtins/string/sub.rs
@@ -97,7 +97,7 @@ fn handle(
                     .out
                     .append(&arg[start..usize::min(start + count, arg.len())]);
                 if want_newline {
-                    streams.out.append_char('\n');
+                    streams.out.append('\n');
                 }
             }
             nsub += 1;
diff --git a/src/builtins/string/transform.rs b/src/builtins/string/transform.rs
index de48f6cef..e7a3c23ef 100644
--- a/src/builtins/string/transform.rs
+++ b/src/builtins/string/transform.rs
@@ -33,7 +33,7 @@ fn handle(
             if !self.quiet {
                 streams.out.append(&transformed);
                 if want_newline {
-                    streams.out.append_char('\n');
+                    streams.out.append('\n');
                 }
             } else if n_transformed > 0 {
                 return Ok(());
diff --git a/src/builtins/string/trim.rs b/src/builtins/string/trim.rs
index aab563754..2fdf55950 100644
--- a/src/builtins/string/trim.rs
+++ b/src/builtins/string/trim.rs
@@ -85,7 +85,7 @@ fn handle(
             if !self.quiet {
                 streams.out.append(&arg[trim_start..arg.len() - trim_end]);
                 if want_newline {
-                    streams.out.append_char('\n');
+                    streams.out.append('\n');
                 }
             } else if ntrim > 0 {
                 return Ok(());
diff --git a/src/builtins/string/unescape.rs b/src/builtins/string/unescape.rs
index 9c3178a88..08f3e5daa 100644
--- a/src/builtins/string/unescape.rs
+++ b/src/builtins/string/unescape.rs
@@ -42,7 +42,7 @@ fn handle(
             if let Some(res) = unescape_string(&arg, self.style) {
                 streams.out.append(&res);
                 if want_newline {
-                    streams.out.append_char('\n');
+                    streams.out.append('\n');
                 }
                 nesc += 1;
             }
diff --git a/src/io.rs b/src/io.rs
index 74319a1e0..a4d37ef2a 100644
--- a/src/io.rs
+++ b/src/io.rs
@@ -717,10 +717,6 @@ pub fn append_with_separation(
         }
     }
 
-    pub fn append_char(&mut self, c: char) -> bool {
-        self.append(wstr::from_char_slice(&[c]))
-    }
-
     pub fn append_narrow(&mut self, s: &str) -> bool {
         self.append(&str2wcstring(s))
     }