You may remember that there used to be a little number next to the post button, it told you how many characters you had left to write. This only occurs on other people's profiles. The screenshot above is taken from kuke's profile, and I tested it with a few others.

^ Screenshot from posting on my own profile, as you can see I have gone just slightly over the character limit.
Could be a permissions error, but I'm really not sure.

Thanks

 

Correct, the top screenshot is from kuke's profile and the next one is from my own.

 

Well then. Sorry for wasting your time >.<