This has been brought up. No I don't believe you should do it, a GM Should. You should report the trolling posts and a GM/Moderator will come and lock the thread and take action against those who made the bad posts. Really from your point of view wouldn't this be better? not only do you get the thread locked, the alleged "Trollers' Get their posts deleted too.
After being on these forums for less than a week I already knew half of the posters here had no idea what the hell a troll was or how to take constructive criticism, They should not have the power to determine when a thread gets locked because most of them can barely have the power to understand how, Just because someone disagrees with you, doesn't make them a troll.
Also, I admit there are some positives to locking your own thread. I.E you ask a question, it gets answered, Problem solved/close. However its the Bads that outweigh the goods because not every OP can use his brain. 9/10 a thread thats locked by the OP goes like this:
OP:"I think XXX would be cool, we should add it"
Others: "I don't like this idea, for xxx reasons"
Others2: "I agree with others, it just seems bad"
OP:"You're all trolls and idiots Im closing this thread"
the problem is simply that while there are 1-2 positives for this power, its overshadowed by the fact people get "power hungry" when they get a taste of power, It goes to their head, and it easily becomes abused.