I think the "close this thread" facility IS useful.
If I had been quicker I would have used it on a recent question of mine(I forgot it was there!LOL)
My question received 30 answers or so.
Only 9 applied to my question,the others were "hijacked answers" that bore no relevance to my original post!
I don't ask many questions,BUT if I do in the future I shall take advantage of it to block "hijackers"
It's really annoying to be told you have got another answer,only to find it isn't about your question at all but some bit of useless banter.