there are comments from 10 different communities

And that is IMO a false problem. It is perfectly okay to have completely different discussions around the same link, just like currently you can have the same link shared on Reddit, Hacker News and other link aggregators and you obviously end up with completely different discussions around the same link.

This whole “there’s too much fragmentation” drama is IMO a false problem raised by people who don’t fully understand that the Fediverse does not mean that you will have one single big entity. It means that you will have something like multiple independently run “forums”, with different vibes and potentially different moderation rules, and users in federated “forums” can easily hop from one to another with the same account. It doesn’t mean that you’ll have one single large Reddit replacement with communities that are deemed “similar” forcibly merged to prevent the false problem of “fragmentation”.

The internet would be in a completely sorry state if only one forum per topic was allowed.