Blogger using feeds from AMO is having problems with feed entry duplication.
"at least in my default aggregator (Thunderbird), the same feed entries are retrieved again and again; I receive each of them at least twenty times."
I believe this person is referring to:
Gen: Thanks for bringing this to our attention. I have commented on the blog you linked to.
I have fixed this issue last month, but it has not been pushed to production yet (see the bug I am duping this to).
*** This bug has been marked as a duplicate of bug 392183 ***