Walk around a house that exists in a non-Euclidean space called a 3-sphere.

Lemmy.ca currently shows 22 comments on [this post](https://lemmy.ca/post/14043), but its native instance, lemmy.ml, [shows 35 comments](https://lemmy.ml/post/84452). It's not (or not only) a matter of only older comments being present, or of comments being from different instances: for example, [this comment from a lemmy.ml user](https://lemmy.ml/post/84452/comment/84632) doesn't appear on lemmy.ca but [this later comment from a different lemmy.ml user](https://lemmy.ml/post/84452/comment/84707) does. Is this a known problem?

I noticed that at the [list all communities page](https://lemmy.ca/search/q/crypto/type/Communities/sort/TopAll/listing_type/All/community_id/0/creator_id/0/page/1) I see many communities from lemmy.ml, but not all of them. The two I happened to notice were "covid" and "crypto". I'm new to Lemmy and don't know what would cause this. I found [this earlier question](https://lemmy.ca/post/6845) but the answer implies at least there's a way for a lemmy.ca user to subscribe to the community in question, and I can't figure out how to do even that. I tried going directly to https://lemmy.ca/c/coronavirus@lemmy.ml but I'm taken to a page that says "Couldn't find community.".