I wish I could force every person who wants to make an online game or social media platform or even a lowly discord server watch this video. It's so good! A dense hour of actual structures and systems! A thing you can do that would actually have an effect, however tiny, on making people happier with each other!
Just to give a taste:
The talk strongly recommends against skill-based matchmaking, because most SBMM queues want you to play against lots of different people to get a good, calibrated ranking. This means you never really get to be around long enough to start thinking of them as people, unless you rank so highly that the pool of potential candidates shrinks to a puddle. This is immediately resonant, at least to me: I have specific, fond memories of playing in tf2 servers, and the best ones often had people that knew each other really well in them. SBMM queues, by comparison, always felt anonymous and a bit cantankerous.
This is of course, not the first time I've had that idea. It's pretty normal to think of SBMM as bad, but not really have an alternative. That's where the video is so good; it can actually provide a useful, practical replacement (if you happen to have the specific circumstances they did). Their alternative is cohort generation. When people start to play, secretly or not so secretly group them up with a largish pool of randoms, and allow them to interact asynchronously. This kind of design is super rare, I had to rack my brain to think of another game that does this, but I actually came up with one: Death Stranding! I know, right?
Even if you can't take all the advice, just because your circumstances are a little different, I really like the idea of rating your designs based on "how friendly will people be in this environment". And that really could apply to so much of modern life, even beyond games.