You may not notice federation lag, where comments don't appear in your instance for some time in comparison to their native or a more populous instance.
Afaik the only way to tell is to pull up the same thread from different origin instances and compare.
A post I made on lemmy.world has an order of magnitude more upvotes when viewed from Lemmy.world compared to when viewed from another instance. Beyond annoying
I think there’s a short delay. But still that would be on the server hosting the post being overloaded. I’m not 100% familiar with how the protocols work. But when I look at top day from sh.itjust.works vs from Lemmy.world the numbers are the same in my feed. So
It must not be a major difference in most posts.
Could also be because of an update not being rolled out to one of the servers. Just a guess.