Why are some translation IDs crossed out?

Translation IDs may appear crossed out if you're using a tool to extract translation IDs from your source code. When an ID is removed or renamed in the source code, it will disappear from the source language translation file, while the other language files may still contain translations for that ID. BabelEdit highlights these entries with a strikethrough to indicate they are no longer in use.

If you've renamed the ID, you can copy the translations to the new ID. If the ID is no longer needed, you can either delete the entries manually or use the "Remove unused IDs..." option from the Edit menu.