[SOLVED] Turn off comments for posts

I have been looking for an option to turn off comments for posts in one of my sites. I have not found it in WordPress, and to my knowledge it is not in Atahualpa as well. Couldn't find a plugin either.

Am I the only one? Am I overlooking something? Or is there an easy way to do this? Would be nice if I don't need to go into the source code, because this gives headaches at updates.

By the way: just to be sure I set all options under "discussion" on the Settings page to off, which includes the "Allow people to post comments on new articles" option. But still, the "Leave a reply" form is shown on all of my posts.