MacOS – Hide username from menu bar

Just ⌘ Command-Drag & Drop it away from the menu bar, this way you can also re-arrange your icons. This trick will only work for OSX icons (e.g. Time Machine or WiFi), for non OSX native icons (e.g. Dropbox or GeekTool) you need a third party app like Bartender or Menu Bar Rearranger.

Another thing you could try would be to lock ~/Library/Preferences/com.apple.menuextra.textinput.plist in Finder. (OS X performs atomic saves on preference files so chmod 600 wouldn't work.)

At least on my account the file contains just a ModeNameVisible key:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>ModeNameVisible</key>
    <false/>
</dict>
</plist>