One reason we discourage posting links to another forum is because we want credit to be given where credit is due. Like Olympia said, linking to other forums can be like stealing someone else's info.
We also don't want to be accused of trying to lure people from other forums to ours. Because we would like people from other forums to respect us, we must act likewise and respect the other forums' sovereignty, so to speak.
We aren't going to overreact or ban you if you accidentally post another forum link. We'll just ask you to remove the link or we'll edit your post to remove it and we'll let you know why. :)
A tip: If you want to post info from another forum, you can copy/paste and cite it by providing the name of the forum and the name of the poster if possible.