This is done on private forums [like OMNI] to maintain your privacy.

Let's say you create a thread called "I hate Bill Smith" and in that thread you link to Bill Smith's website.

If someone clicks on that link, they will show up in Bill Smith's website's referrer logs as coming from the page http://www.flyertalk.com/forum/123456-i-hate-bill-smith.html. When Bill goes to investigate, he can't follow the link because it's a private forum. Drama ensues, and long story short, someone posts in the technical issues forum that we should obfuscate outgoing links in private forums.

As a web developer, I would not recommend disabling redirects to anyone. They are a very common practice and most often done for the user's benefit. If a thread here is moved, for example, we want to make sure that users are still able to find them, so we leave a redirect. If we rename a forum, all of the links to that forum will be broken, so we put in a redirect. This isn't because we're trying to do something mischievous-- we do it for the user.