I'm having a related issue - I think. I'm putting this here to help anyone else who encounters this issue and doesn't want to spend hours/days/whatever figuring it out.
I'm using Gmail, so that's established.
I had my account set to send me a copy of all of my messages.
I was receiving TWO copies of my replies to others, but not necessarily my own posts. It turns out that I was getting my Gmail copy of my sent message ALONG WITH the copy sent by GIO, so each reply I sent was showing up twice in the threads to which I was replying.
I unchecked that setting, and now I'm getting nothing (initially) on my own posts and only the Gmail "Sent" copy in my Gmail threads.
