Recently I gave a cryptical comment to an answer and I wanted to follow up and check whether the answer had been updated following my suggestion. It turned out I could not find my comment on my activity page. I could trace the question, by searching for it, and it turned out the answer had been deleted (a drastic consequence of my comment?). It was still visible but grayed out or so.
Isn't this a little strange, that comments are unlisted from the user page? I would expect them to stay, perhaps with a note that the answer or question was deleted.