There's no easy answer to this. A billion different places users could go doesn't mean they have active communities, and if I mentioned where I like to hang out on the internet, those areas would probably get ruined.
Instead, I'll mention two platforms some of my friends like, to avoid taking the cost of a ruined platform myself:
sqwok.im: This one is the most microblog-like of the two, but it's also the least conventional. The quality varies; the front page only looks good every once in a while.
tildes.net: This one is invite-only, which helps mitigate the masses jumping in somewhat, and is run by a former reddit administrator. The existing community isn't great, but it's good. Friendly enough people.
Instead, I'll mention two platforms some of my friends like, to avoid taking the cost of a ruined platform myself:
sqwok.im: This one is the most microblog-like of the two, but it's also the least conventional. The quality varies; the front page only looks good every once in a while.
tildes.net: This one is invite-only, which helps mitigate the masses jumping in somewhat, and is run by a former reddit administrator. The existing community isn't great, but it's good. Friendly enough people.