Each post's character limit is 10,000, but since that counts BBcode styling some of the longer posts (character apps) will probably come up either around or above that.
The one I've posted for instance, comes up to ~9,700 characters not counting any BBcode and ~11,100 with the BBcode.
Perhaps raising that limit to 15,000 or even more could be done? The app I've posted isn't all that long, given older standards.
Edit: Maybe the [SIZE] tags could be changed as well, if that's possible? The max size, 7, is hardly large at all. (Setting it to higher than that will just revert it back down to 7.) Maybe there another way to size the text that I'm ignoring though, like X px or something.