Here's the thing. I'm a mod for a small-time community for a niche interest, !castles@lemm.ee I'm also on Mastodon, and was before my Reddit exodus. I follow #castles as well as a few other related topics on Matsodon, so I get quality toots, such as this: https://mastodon.scot/@McNige/110926238926867959, that I wish I could just crosspost over to my community. Currently, I have to repackage the toot, which isn't a huge problem, but currently I just drop them a note on Mastodon that their content has been posted elsewhere on the Fediverse. What would be nice is if people who comment on the Lemmy post also get fed into OP's toot. More sharing, more connection, more activity.
On the flip side, I've subscribed to @castles@lemm.ee on my Mastodon instance and, while it's good to be able to follow posts in feed form, it looks like ass: 
I realize I should try this with Pixelfed, but I haven't made that leap yet.
I don't know, am I thinking crazy here? I'd think we'd want everything in the Fediverse soup interoperable in a more seemless way. Is this a feature request or am I missing some way to do this better?
Nah that's not it. It's just AP is extremely broad and Mastodon only cares about a hyper-specialized subset of it. AFAIK even with things like writefreely (which serves Page objects as opposed to Note objects which are what Mastodon uses for microblog posts) it first "converts" them to extremely long Notes and then handles federation that way.
From what I know other implementations such as the *omas or Friendica are a bit more lax and generally have wider compatibility with non-microblogging AP.