EDIT: Are embedded images also counted as characters? How about URLs? If they are counted then it's possible that someone could insert 1x1 pixel images or single character hyperlinks to their posts to make it look as though it's longer than it actually is.
The thing is that people who do this aren't really going to last long at it. Sooner or later someone is going to hit "quote" and then "WTF are all these images?" and then busted. And then you're going to be in a lot of shit because you're clearly trying to game the system. It's really pretty foolish, IMO. I mean you may get away with this silliness for a little bit of time but in the long run it's clear that it's going to cost you a lot when you consider all you could have made by not getting negative trust and removed from the campaign and labelled as a cheater.
Any technique that relies on putting weird stuff into a post so that a bot will read it is going to fail in this way as soon as someone clicks the quote button.