If I visit a community from Feddit and then another instance, the comments often differ. I understand there are some issues with defederation between some instances, but this doesn't seem related to that.

For example, here's the post-race discussion on the Formula 1 community on Feddit: https://feddit.uk/post/320484

And then the same discussion on lemmy.world: https://lemmy.world/post/950479

I don't understand why a significant number of comments aren't visible on Feddit.