That’s something (interesting) to unpack but wouldn’t belong here. Anyhow for the sake of my personal benefit I proceed to comment.

You answered everyting per se. So thanks.

There is a connection between a lot different Software Platforms on the Fediverse, but not every feature is on every plattform. So you are not able to downvote a Lemmy post from Mastodon.

Makes sense: Mastodon does not have downvotes, apparently. But:

You have the option to interact with Lemmy posts with a Mastodon account …

Is this also valid the other way around? Are there peer-reviewed documents I can inspect to learn how the fediverse can act between another? I did not look into the protocol since standards wouldn’t address my higher level view I suppose.

I have never used the Mastodon app, i think a lot 3rd Party apps are better on Mastodon, so i don’t know how it looks, but Mastodon has, or had, a weird form in showing commet trees in my opinion.

I downloaded the fediverse app prior but it didn’t allow sorting either. Which is why I made the above assumption.

The mastodon app appears to be a very good piece of software; Better then the former.

The app doesn’t allow opening links from any source but it appears to me that they do not want to provide a wildcard intent (android-API specifica) so that to be mentioned when tapping any link. A thing which have to be implemented at build time and would possibly still leak private instance domains. It looks carefully engineered.