It's awkward for me because the comment feed feels very segmented. It's awkward to have a big header for a smaller/niche instance and one comment below it.

It makes that comment seem like an orphan and gives prominence to people who use the biggest instance.

I'd also want the sort I apply (Hot/New/etc) to apply to every comment, not per instance.

I'd propose something like this.

Clicking on the Server dropdown could be a simple checkbox group, which would remember your configuration across that instance. That way, if you wanted to hide specific communities from appearing, you could.

Halp

Wow what crazy timing, must be a coincidence

Had a blast with the demo thanks for reminding me it's out