For me, the problem with tweets is they're too short to provide anything useful, at l least in terms of TextMate tips
Likewise the mailing list isn't really an appropriate arena for them.
New TM users are very unlikely to search the mailing list archive to find tips, so it would only be helping the userbase who were subscribed at the time of posting
I'd much rather see a wiki, which everyone can contribute to, and develop it into a good TM guide.
Right now the docs are a little outdated and ambiguous, with many articles referencing TextMate 1 (but not always making this clear)