Thanks for experimenting with this! I have only spent a short time working on Mastodon integration as the main priority is Lemmy, Kbin and any other ActivityPub-based platform that has following of groups / communities (not just people). In Peertube, for example, each channel is a group so it would work well to have PeerTube channels show up in PieFed as a Community. Each video in the channel would be a separate PieFed post which can be replied to, etc. The way peerTube works translates fluidly over to PieFed, so I feel the effort put into making that work will be well worth it.

There is some good news though. If you get the URL of a post from PieFed, e.g. https://piefed.social/post/4469 and put that into the search field in your Mastodon instance, the post will show up and you can reply to it from within Mastodon. This only seems to work for posts made in local communities, not something originally posted on, say, lemmy.world that was federated to PieFed. It's a start.

I'm sure Mastodon integration will get more attention in the future as it's user base is very big, however for now the focus for me is on Lemmy and Kbin.