Maybe not the right place for this, but why is gxs's comment dead? It's factually correct (as far as I can tell), and provides more related reading material.
There isn't really any way to ask for reinstatement except to email pg - that's if the person even realizes their account killed, since the system conceals this from them.
It may have happened because initially when I edited the comment for a typo, it displayed duplicate comments after I hit update. So naturally, afterward I deleted one of them. My guess is I got caught by some spam filter or something.
For what it's worth, my original comment was just pointing people to Matthias Wandel's site: http://www.sentex.net/~mwandel/ where he actually has lots of cool projects. In particular I like the marble machines and his demo on how combination locks work.