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

Lemmy.ca currently shows 22 comments on this post, but its native instance, lemmy.ml, shows 35 comments.

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 doesn't appear on lemmy.ca but this later comment from a different lemmy.ml user does.

Is this a known problem?

I noticed that at the list all communities page 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 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.".