The E-mail settings bug has been fixed already before
Since this seems FreeFlarum related only, I will look for error logs and report them. I should have time today, so we'll see
Edit: I've tested it and it works - the post gets flagged for approval (so the approval extension must be enabled), for users that don't have admin. An E-mail is sent too, and merging works correctly too (tested at https://beta.flarum.cloud, word "eucalyptus", feel free to test it all you want). And obviously, no error logs (since it works).
Also note that the "awaiting approval" message is not visible for the post author. And you can't test it with admin account, as I am pretty sure that the filters don't affect it