That's the thing, I haven't blocked anyone. Even in this thread I see your comment but another user also replied to me but can't see their reply in the thread but I only see it in my inbox. Strange.
I was going to suggest you might have bot posts turned off, as that seems to confuse the UI. But the other reply is not from a bot, and it's not a federation thing either since you and I are on the same instance and I see it just fine. Interesting!