Concerning editing posts.... The way i run it on my board is there is a mod that allows you to specify an edit time... That way if someone actually DOES need to edit it for a mistake, they can.. but after 15 minutes, they can't touch it.
Be warned that the latest version of phpbb is going to be a HUGE overhaul, and the coders are saying that practically no modificatinos will work with it.. everything will have to be re written. Evidently in the early stages of builing phpbb2's databse, they didnt build it in a way that would be ideal for handling huge loads on the database, so rather than continuing building on a crappyer code, they are redoing stuff. This is why I haven't updated mine, and wont until the new phpbb comes out.. Which will have a lot of new modifications to it anyways.