Yes, ideally you‘d want to have a few large communties on each instance and not all topics with a single userbase on one. This not only decreases the load but also prevents scenarios in which a single admin starts to capsule their instance with a large userbase away from the federation.

Sounds like a good solution. To make the colors less invasive it could only activate once two different users with the same name comment in a single thread.

Just until someone starts vomiting in places other than the toilet. In many cases it‘s better to be invited than to be the host ^^