When checking crypto's suggested edit queue this evening, I saw a suggested edit for a tag wiki that needed improving, so I went ahead and did it.
This presented me with good old Pagedown, however, unlike the tag wiki except editor that usually presents itself, there was no character limit. You should be able to see this here. Further edits from the tag wiki page show that we've clearly exceeded the limit!
I take it this is a bug?
Edit: as a question, I'm not quite duplicating... but I suspect it is the same problem as seeing the CW checkbox, no?
Edit 2: this appears to make strange things happen with the revisions, too. Take a look at the history tag, then take a look at the revisions. The revision that's being displayed for the tag... isn't listed. So being able to exceed the limit does bad things.