When wikitext editor with CM is closed, the user is asked to confirm even if no changes were made (e.g. when copying refs from another article). It doesn't happen with CM disabled.
Topic on Extension talk:CodeMirror
I can report this on Chrome/Mac also. Interaction with the text (highlighting and copying etc.) triggers a request to confirm when you close the tab even if the text has not been modified.
Yes, this is a problem that we're going to fix -- the bug ticket is phab:T177175, if you're interested in following it.
Thanks for reporting the bug.
No problem. Just to stress, I'm very happy to see syntax highlighting and am an enthusiastic beta tester. It really makes finding your place in text much easier.
That's great, thank you for saying so! It's been really helpful for me, too. :)