Have a look in
templatesdefaultxs_topic.tpl
Thank you! That's exactly what I was looking for.
Do you know if that file also controls the buttons for private messaging?
Edit: Nevermind it's right there on privmsg_read_body.tpl . However, it'd be useful to know where the private messaging images are because I'm having the same problem with REPLY_PM_IMG
Edit (again): Well I only found that REPLY_PM_IMG code in privmsg.php and since I'm not going to change php for a template I'll just use the old markup for the PMs. I think you can mark this as solved