In the long series of things we all live with and tend to overlook...
Not only does the editor insert newlines and force the cursor to the end of the line once in most messages, but sometimes it loses edits.
For example, make a post, see a typo, go back to edit, make the change very quickly, then repost.
If you're quick about it, the change is likely lost. The more coffee, the more likely.
I think it may be that you have to edit a post for a certain amount of time before the edit is accepted, but I'm not completely sure. Maybe this is the same amount of time that normally elapses before the newline/end-of-line thing. Maybe this is some kind of misguided security feature or protection against double posting - I don't know, but it's damned irritating to have to do things twice!
Until very recently, I had not encountered the Edit Bug, but have now experienced it twice, though before Read Tracking came back. Now I know what others have been complaining about. Guess that I need to do my edits, BEFORE I post, or maybe be slower about doing the corrections.