How much of this works with Mastodon and Pixelfed?

How much of this works with Mastodon and Pixelfed?
Hi, @AskKbin community! (ง ื▿ ื)ว
I created a couple of groups on a #Lemmy instance to see how well they got along with #Mastodon & #Pixelfed. Even though I could create posts from Mastodon comments made from Lemmy were invisible to Mastodon users and vice versa.
I like the fact that #Kbin allows tagging contents in magazines. Is there something else I should know to post from other socials?