While I was working on a edit (revision 3) somebody else committed revision 2, fixing the typo in the question title. This prevented me from saving my edit, clicking on "Save Changes" repeatedly just informed me that somebody else edited the post title and that I should start my edit again from scratch.
To get my changes committed I had to open a new edit window and copy-paste the post contents there.
I should be able to just save my changes anyway, if I think its an improvement over the previous edit.