I just tried to post text and pic to a thread and it said too many characters. So I changed it to an acceptable number of characters and it still wouldn't post and got the same message. So I posted it in another thread and it worked. Once you've put something in the reply box it sometimes just won't go away no matter what you do. I would say that's a problem.
In a case like that, it's most likely because you have a saved draft in the reply box. If you click on the icon in the toolbar that looks like a floppy disk, you'll see the option to delete the current draft.
Tried it. Didn't work. Deleted drafts and tried to post something else. Got the same message that it exceeded three thousand characters.