I have a wordpress.com blog. Anytime I comment on other .com ones, it all goes through just fine.
I happen to read a lot of blogs that I'm pretty sure use wordpress.org. I've always been able to comment on them until a few months ago, and now my comments never show up. If I try to submit them again, it says duplicate post detected, but the post isn't there, and I know I don't need to go through spam filters because my previous comments have been accepted. I can check weeks later, and my comment still won't be there.
I really doubt that the entire Internet has decided it doesn't like me and is blocking me. And it's happened on more than one computer. What gives?
(some of the many blogs that I can't seem to comment on anymore: thebooksmugglers.com, ala.org/yalsa/thehub, malindalo.com, publishingcrawl.com)