Considering Carmack's tweet and Facebook's response, I'm willing to bet that Carmack (being the smart guy that he is) just re-wrote the code that Zenimax may have had claim to. In programming, TMTOWTDI, which would make Carmack/Facebook's claims true while making Zenimax none the wiser, thinking they might have a claim against Facebook.
The RFC says brackets are reserved, so they should be escaped... and it looks like the URLs in the feed are actually encoded, it's just the browser is decoding them for you when you're looking at the page. If you look at the source, you'll see:
Brackets are technically valid in a URL. I saw a screenshot of DoggCatcher in another thread, and it looks like there was a java illegal character error. I think the author of the app needs to escape/encode the brackets or quote the URL string, so I don't think the error is on GiantBomb's side.