If anyone votes on an old comment from the source instance, your newly subscribed kbin instance will grab the older message when the new vote comes in. Works with both Lemmy and kbin sources.
If the comment voted on is a reply to a reply, it will load in all the parent comments as well.
If you have a login on the other instance, you can vote and unvote and it will still populate your kbin comments.
What’s the “Fediverse icon”?
For lemmy it’s the rainbow coloured hexagon on a post or comment.