This would not prevent account sales, as one could easily do it in private or on a external site. I don't see it being a bannable offense anytime soon (even though I would not mind it).
I guess I don't understand this argument. It seems more like clinging to the status quo that, at least with respect to account sales, is broken. The sales may very well take place outside this forum but by banning them here it certainly makes it more difficult, for buyers and sellers. This is common to a lot of forums that I've seen: actions that are frowned upon are not allowed on the forum, period. It makes no sense to me that the community is giving red trust to people for these actions that are perfectly within the rules of the forum.