I think this is a bad idea - it promotes the notion that the first poster somehow "owns" the thread, which is quite clearly not the case.
I think the only people who should be allowed this kind of privilege are administrator and mods - it is only Paul and whoever he nominates, who actually "own" the space.
Secondly I think it is open to abuse - so somebody can post something controversial or misleading, then lock it so nobody can reply and correct the false impression given - they can go round doing this multiple times, creating the impression that nobody disagrees, when they just haven't been given the chance!
It would be like a "field day" for Trolls!!
I think it is quite sufficient that thread starters can delete their opening post and thus get rid of the thread from view causing no aggravation - this is all they should be allowed to do!