On Lemmy: no, not really.

On the Fediverse in general: if a user on your server replies to your post and submits that activity to their followers (be it the Lemmy community they’re operating in, the community they’re responding to, or the public timeline), the original post is also repeated. If a Mastodon user were to follow you, their server should receive a copy of the threads you’re responding to.

This is done to prevent “ghost replies”, responses without context appearing in other people’s timeline. Replies don’t always need to be a note, for example; if you like or favourite a post, other servers will receive a message basically saying “@[email protected] just liked post example.org/post/2109912310257320932479324” which is completely meaningless if you don’t know what that post is referring to.

You can find the exact details in the ActivityPub specification (warning: technical document).

The specification describes how posts are repeated from someone’s inbox (the stuff you’re following/subscribed to) to their followers. Lemmy doesn’t let you follow a user, so this is mostly meaningless here.