People are saying they don't like the spam, it's ultimately the choice of the user if they do not want to see repeated posts of the same item.
I get posting to 2 communities of the same, but if you are filling multiple communities with the same post. You aren't really adding anything. With the fediverse people can subscribe to multiple communities with what you're suggesting, if everyone were to spam posts, which this is what it is. It's spamming the same post across multiple communities. What you're going to end up with is a bunch of redundant communities with a severe lack of orginal content. Which harms the community they are posting to more than it helps.
Why should I subscribe to both News@lemmy.world and News@SmallLemmy if the small community is just reposted content from the first community. I get what you're trying to say, but this kind of thing harms the communities more than it helps
They can do this if they want too, but I'm not going to bother subscribing to a community with duplicate posts. That's not the point of the fediverse.
The beautiful thing about Lemmy is you can have multiple communities co-existing, producing their own unique content and be subscribed to all of them at once. Nothing against cross-posting but this doesn't feel at all an organic way of sharing content. It feels forced and hampers discussion.
People who are scrolling through all can see these posts, and will need to pick between 3 of the same post if they want to discuss it, It will spread comments thin. It makes more sense to just post it to one, then maybe wait before posting it again to another community.