Adjust the spellcheck language
MacOS has a system-wide spellcheck feature. Fortunately, this can be adjusted by the user. Glenn Fleishman shows how
Since the spellcheck in macOS is systemwide, you should be seeing this in more than one application if it’s happening in Facebook via a web browser. There is a language setting for your Facebook account, but it doesn’t seem to interact with spellcheck, which is a system function. Further, if you change your Facebook language, it changes
its interface to use that language, which would be obvious to you.
You should look in two places to see if macOS preferences changed:
• In Safari or any app that lets you type, click in a field or a page to get a cursor and then select Edit > Spelling & Grammar > Show Spelling and Grammar. This floating palette may be set to Automatic by Language. Set it to UK English and see if that solves the problem.
• In the Language & Region system preference pane, English/English (UK) should appear at the top of Preferred Languages. Drag it to the top of the list if not. You can remove any other languages that you don’t speak or want to appear.
Failing that, you can disable automatic spell-checking within Safari (or any app). In an app, choose Edit > Spelling & Grammar > Check Spelling While Typing and Correct Spelling Automatically one after the other to remove their checkmarks.