It sounds like a cool idea, but I have my doubts:
- Security: contributing code in a wiki and executing it on the server sounds like a very bad idea in terms of security
- Usefulness: why the heck do you need to run arbitrary code on a wiki page?
- Maintainability: There's a reason why code and templates are usually separated, and that is maintenance.
That said, I'm sure it's a very nice proof-of-concept demonstration of what parrot is able to run, or hopefully will be able. And adding wikicreole markup to November is certainly a very good idea.