It's possible, but we felt it would cause chaos on the format that would overall be ugly. Yes, having your own personality shine was nice in a sense, but it also contains a lot of clashes to the design of the forum's layout. People will have all sorts of colors, borders, sizes, etc. For your little taste of personal flare, the forums begin to become an eyesore in some cases.
I said the same thing to Alex when we first moved over, but now that I'm used to it, I actually prefer it without. You still have plenty of means to personalize yourself via your own profile page. But, you can always put up a poll and see what the masses say. It is an available add-on that can be implemented.