@Mike Linksvayer Not an issue list, but here's y two cents:

@Sumana Harihareswara posted via Identi.ca web, only to followers (if you refer to this post: https://identi.ca/brainwane/note/OAroRQm4QvythaKzcRtZpw

@maiki is not following Sumana, so e didn't get the original note, only saw the note when @Mike Linksvayer shared it.

And here, we arrive to @JanKusanagi's explanation.

So in fact, I think there are two issues:

If A send a post to followers, and B (following A) shares it, the post arrives (via "meanwhile") to some people that follow B but not A.
When you see a post via the meanwhile tab (because somebody shared it or liked it), but in fact is a leak, and the original post was not intended to you, you'll have troubles to participate in the conversation.

But (1) I'm not sure I'm diagnosing well, and (2) I cannot point to a particular issue when these things are reported. I'm too tired now to search the issue tracker, sorry.