I really couldn’t care less if I can follow a Lemmy community with my Mastodon account or comment on a PeerTube video with my Lemmy account.
Don’t get me wrong, it’s neat and a cool achievement of the ActivityPub protocol, but that’s like advertising that your awesome new solar-powered, self-driving, flying car also has power windows. I’m glad it’s there, but there are way better things to talk about, especially when trying to convince a newcomer to jump on board.
The Mastodon posts are nearly always higher quality and more on topic than posts from lemmy users.
At the very least, simply mentioning a community shouldn’t result in a post here. There is no shortage of “Just installed @[software]!” posts with absolutely nothing of value.