I want to buy links, which Subforum should I go?

Yes, you are right.

By the fact that "bought links" look unnatural, arise in large numbers and tend to be on non-context-relevant pages.

I hear Google saying it, loudly and clearly and repeatedly. On websites and blogs and in videos and under the sea and on top of the mountains and at conferences and every time they get the chance to clarify it.

And I see all the threads started off (here and elsewhere) by people who have had their sites' SEO hammered by the Penguin update and are wondering why, until people ask them whether they've bought any backlinks recently - and then sometimes the penny drops. You need only look through the SEO folder here (and/or elsewhere) at the people whose businesses have been hammered by Google's Penguin update and told openly by Google that the reason was that they seemed to have built unnatural/automated backlinks, to want to stay away from that possibility.

It does, regarding this subject. Backlink selling is permitted, and is happening, in this forum. (It used to be banned here, at one point, but not now).

Murphysmurfy may have been too outspoken (ok, he was too outspoken) but ultimately he's right and you're wrong, and that ought to count for something, because you can learn something from him, if you're willing to overlook his momentary outspokenness. And to answer your original question about subforums, this is the one to discuss backlinks: Adsense / PPC / SEO Discussion Forum

These threads may help, also ...
http://www.warriorforum.com/adsense-...ml#post6021235
http://www.warriorforum.com/adsense-...-services.html