Please make message size limit configurable like other permissions.

I don't want everyone to be able to post 2000 chars. For some people, rather than kicking them, it would be better to limit how much they can post, etc.

Although smaller message sizes can be annoying, they can also encourage conversation instead of book writing, especially in cases where people in a conversation write short messages and one person _always_ replies with a book.

We need some control over this in certain cases.