It seems probable that we have at least one Serb, Bosniak, or Croat above age 45, which puts them at a high likelihood of having participated in genocide.

Does this count forced sterilization/abortions or even something like a high tax on babies in certain ethnic groups with the aim to decrease r to be close to 0?

I do think it's very unlikely even so. We're banned in China, and I expect the same of other high tech, authoritarian societies. We did get a lot of traffic from Russia though early in the Ukraine, but I suspect we'll be banned if we get too popular.
(And we're not approachable / easy-to-use enough yet that low tech wartorn societies are likely to have manifold users. Some modern terrorists have a social media recruiting strategy, but use the biggest networks since the goal is advertising rather than discussion/learning)

@Sinclair I would not count sterilization or a baby tax, because that's not killing someone, it's just preventing them from ever existing.

Abortion I guess would count, yeah.

@IsaacKing Then I think you might want "genocidal mass murder" as your criterion, then, because "genocide" has an actual international-law definition and yours is much narrower.

@Lorxus I'm using the definition from Google, which I think is pretty well-accepted?

@IsaacKing If someone here decides to voluntarily have an abortion because the fetus has Down Syndrome, would that count as participating in genocide? I know some people who would consider it that.