I see lately lots of answers like this that use joke “languages” like HQ9+. Should we add a requirement that the language should be sufficiently complex?
This is just my opinion as a user, not as a moderator.
I think HQ9+ is more or less grandfathered in. Its applicability to most golfing challenges is very limited.
As for new languages, I'd like to see languages that are general-purpose and not tailored specifically for a certain class of programming problems. For example, GolfScript is actually general-purpose and it doesn't have special backdoors that give you a one-character solution to Hello World (for example).