Because you can't control human beings? I'm not entirely sure what you mean. The entire reason the structure of ActivityPub and the Fediverse is what it is, is to have moderation not controlled by a single entity. Enforced consolidation is both impossible and would defeat the purpose.

Lemmy "communities" are structurally just modified user accounts. So it seems like it could be possible for one to "re-toot" a post similarly to how it can be done on Mastodon and elsewhere.