How do you close a discussion?  

I wondered the same thing. You cant delete you past questions. They just move down the line and no one looks at them, or they get moved off the site.

You close it by selecting a best answer.

look across the top, click discussions, then discussions I started, then under your avatar you should see mark this best reponse.
So it's not really closed, but they know you done picked best answer and probably won't be viewing that thread again.

i dont know however let it be it doen't matter
as may be anyone can atl;east not now then whenever can reply ur topic by searching
so let it be man
never lose hope

if you want to get rid of them and they have no responces i think that you can emaiol mylot and ask them to remove it

I am surprised they haven't edited the 'adult' picture you have posted. Anyway, I posted something like this before and it disappeared. I never did get any responses to it. So I don't know how. (Seems to be a 'knack of mine!) If I could get going with this Randpoly thing, I would close my discussions also.

i need to close a few of my own posts too lol

I have marked the best response but still Im getting the response...