It seems to me, your gripe is not with the chat system stopping you from 'spamming' messages to quickley, but from your longer posts being shrunk down with a 'show full text' link at the bottom.
I personally think that current system is just fine. Normal flow of conversation is not halted by the anti-spam filter, if we can accept calling it that and long posts are shrunk so that they do not get in the way.
A long message will break up the chat, as it very quickly pushs messages of the screen. The 'folding' of it prevents this, to a point, but allows users who actually want to read your entire rant post can.
I think the ideal solution, is to allow users to configure post folding. Thus you would be able to disable it for your self, without forcing us to have look at your big fat wall of text.
EDIT
I agree with the anit-spam filter at low levels, if anything, it should have an even longer time out. It helps force people to think a bit more rather then use chat as a stream of conciousness. But like as people reach higher levels of rep, there is no need throttle them in such a fashion. If some one did decide to go wrong, a ban can be applied easy enough.
So yeah, an unlock of "you can now spam chat, but don't" would be a good idea.