… there is a 300 character limit, and when you hit it, you can't type anymore. A better UI would be to allow the user to type more, but indicate that they are over the limit, and not allow posting until they get it back under. This allows getting your full thought out and then trimming throughout the piece to fit the limit. This is how Twitter handles its character limit, and it's much more user-friendly than simply disallowing further typing.
When adding a premise, for instance:
http://en.arguman.org/semi-colons-are-unnecessary-in-javascript/premises/28292/new
… there is a 300 character limit, and when you hit it, you can't type anymore. A better UI would be to allow the user to type more, but indicate that they are over the limit, and not allow posting until they get it back under. This allows getting your full thought out and then trimming throughout the piece to fit the limit. This is how Twitter handles its character limit, and it's much more user-friendly than simply disallowing further typing.