Hmmm .... Probably a good thing, though I haven't tried it out in real life yet. I suspect that it will have difficulty with correct spelling (as opposed to that heretical American stuff), and that that problem will make it something suitable only for occassional use unless you are from the USA or points nearby. (Indeed, to try it out right now, I could suggest that it a horse of a different colour.)
On the whole, I think it would be much more useful to simply allow members to edit posts.
Hmmmm ... unless "occasional" above has just one "s" when I post this, it doesn't work. Probably doesn't get on with the always-suspect Java support of Opera 6. (I have not yet warmed to Opera 7, despite spending money on it. Seem to use 6 most of the time.)
And yup, it doesn't understand "colour", nor offer it as an alternative to the unlovely "color".
A very neat mod, and certainly worth the experiment, but all in all, editing posts would be a better one.