From design point of veiw:

1. My commennt / clarification / what_ever is definitely not an answer.

2. If you call it "posts" instead of "answers" this will be less confusing (in my oppinion).

 3.You may create user preference: "count my answer as reply" (Yes / No) and the user will choose according to his preferences.

4. You may create two fields to show:  aswers and posts. Posts will contain all the posts in this thread and "answers" only non-mine posts. As an optimization, "posts" statistics will be shown only if you already commented you own post (meaning number of own post >1)