OP won't see your image unfortunately, because of a difference in how embeds are handled (Mastodon's use of image attachments to Lemmy's use of MarkDown has been fixed in one direction, but not the other).
@mho@fediverse When viewing the post on pixelfed.de I can see two comments from pixelfed.de users and one from pixelfed.social, yet I don't see them federated to Mastodon or Lemmy.
I think you misunderstood the request to "share" there. They're most likely talking about boosts, Mastodon's version of Twitter's retweets. Lemmy, I think, doesn't implement boosts. So it makes sense you would interpret it differently from the rest of the fediverse.
Basically, this isn't a call to repost. It's essentially just asking to upvote and boost and OP can then see from where those interactions came.
why should I not remove this from !fediverse?
It's on topic and your community has no rule against test/experimental posts.
Your community might want some additional rules if these kinds of posts are undesired. Like a low effort rule maybe. Or a rule against posts asking for upvotes and similar actions. A quick look at lemmy.world's site-wide rules didn't look like such a rule is there.
@mho@fediverse noice ! I was thinking about creating something similar, but it's seems that I'm a bit to late. If we want to counter Meta and offer decent EU social media, agnostic broadcast protocols are a key element.