Updatev2: I think I may have interpreted it wrong, PG wrote "Someone who has a pending comment will have to wait till it goes live to post another" so I guess all comments will be pending but after being endorsed once can comment again?
^This makes a lot more sense to me than the one comment at a time idea. It gives people some slack and if the community decides one of your previous comments was unworthy to be in the official discussion thread, there's an incentive to delete it but also not too much time pressure on the part of the endorsers in the community...and thus on the commenter.
I predict this will reduce inane back and forth flamewars.
Update: apparently this comment was still pending http://i.imgur.com/KBuY5fx.png
Updatev2: I think I may have interpreted it wrong, PG wrote "Someone who has a pending comment will have to wait till it goes live to post another" so I guess all comments will be pending but after being endorsed once can comment again?