This is somehow a continuation of my bug report Comment appears in the inbox, but not in the responses (with the exact same title, but the previous bug was fixed).
Yesterday I got 4 comment @replies from Gilles in my inbox, all on the post How do comment @replies work? Some of those comments are edited and didn't include "@Hendrik" when they were first posted, but some contained "@Hendrik" from the very beginning. However, none of the comments appears in the "responses" in my profile's "activity" tab. (There are only 2 entries for yesterday in the "responses", both of them comment @replies that came due to others using "@Hendrik".)