Does the Battle of the Bits forum count? There are some extremely serious and quality discussions like this one 
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Seriously though that place's pretty much integrated to the very own website, which is dedicated to music battles and competition with a tendency to go into chiptune stuff (although other formats are allowed too), it exists since fucking 2005 and it somehow still exists.
Oh and i also used to lurk on other forums, had an account on one of the many places that are or were communities centered Super Mario Bros X when i was 13/14 but didn't post much.
