I've noticed this before. Bit of bugbear.
If I get a little enthusiastic with my verbiage and overflow the character count, of course, I receive a polite message to that effect. However, if I then edit the text to come within the prescribed limits and click "save", nothing happens. The site goes off into some cyber neverland and I can't get its attention without cancelling the window, which, of course, deletes my text. All rather frustrating.