There’s a significant distinction between servers that are actively malicious as you’re describing and servers that aren’t fully compatible with certain features, or that are simply buggy.

Lemmy, for example modifies posts federated from other platforms to fit its format constraints. One of them is that a post from Mastodon with multiple images attached will only show one image on Lemmy. Mastodon does it too: inline images from a Lemmy post don’t show on vanilla Mastodon.

I’ll note that Lemmy’s version numbers all start with 0. So do Piixelfed’s. That implies the software is unfinished and unstable.