Technically, when you post on the forum, the copyright is the board's. This is logical, because you could not expect to come back in 5 years and tell us: "remove my intellectual property."
However, because I value people's rights, I have stated on more than one occasion that I grant users an unlimited license to reproduce their own posts elsewhere. It just seems like the moral thing to do, even if US law does not require it.
Regardless of who is the copyright owner, copying sections of a work in order to comment on them is covered under "fair use."
Regarding taking a post and commenting on your own blog: I don't have a problem with that, as long as our content is not being used solely to bump up one's blog's content. Linking helps our SEO with google, etc., and helps other people find our site.
While we cannot legally stop anyone from doing this, we would ask that you not create posts on a blog solely for the purpose of attacking the person of a poster or profiling a poster, etc. If I found someone doing that, I would attempt to find creative ways to deter that poster from doing it.