That’s true, but to be honest there’s already a pretty good verification system on Mastodon, even if you don’t host your own instance.

It’s a generic ActivityPub client.

It works this way because Mastodon and Lemmy both implement ActivityPub.

When you mention a Lemmy community from a Mastodon post, this post is sent to the Lemmy server you mentioned and treated as a new post in the community by Lemmy.

Then, when people reply from their Lemmy client, these comments are also visible to on the OP’s Mastodon server.

Automatic conversion to Kepub is a benefit Calibre has, but the same thing can be done by running Kepubify before copying the files manually.