What query would I use to count for a user the number of times their post was the second one in a thread (eg the first reply to the thread)??? I didnt find a field in the post table for this.

don't know if it is possible at all, querying the number of replies he made in total is possible (total posts - total threads started)

maybe someone else knows how to do it?

Well, I believe there's a certain code in a query which picks only the second (or third, fourth, etc.. its defined in the code itself) result in the query. I don't know how this works though.

Theres no one query for this, you would have to baslicly create a script with alot of queries and conditions to narrow it down to that. It's possiable, just would be very time consuming to create and figure out.

.. and very resource intensive.

wouldn't it be possible with the query that gathers the info for creating that numbering of the posts in a thread? (upperright of a post: #6) (postcount)

Thats what I was thinking, but I couldnt find any info on it. Tired looking at code in showtread.php, but couldnt find that query.

have a look at this:
showthread.php