The problem with the [non-lisp language] community is that they don't have a sense of humor.

FWIW, I didn't think so at first. After reading a few of more of Shivers' writings linked here I get it, but initially it comes off as crazy.

Joking about one's self is not necessarily self-deprecation. You can exaggerate things for humorous effect in a way that's only partially deprecating, or even not at all. Without knowing the author, it may be hard to tell.