why is this 2 year old post being shown? Is it the way lemmy works? I find it interesting

I think its because there was that comment on this post a few hours before yours, so it was pulled into the active feed.

by “active feed” you mean when we sort by active posts? I always sort by hot.

Yeah, I think Hot also has some similar parameters as Active. I have no idea of specifics so just a guess but I think Hot is pulling in threads that have any sort of comment activity on them or new upvotes? Idk