During one of their usual exchanges Fenris says something particularly cutting, and when Anders doesn't reply, he turns to Anders to gloat about finally getting the mage to shut up... except he sees that Anders stopped talking not because he couldn't think of anything to say, but because he's tearing up. Fenris has absolutely No Idea how to deal with that.

+ someone comforts Anders without treating him like a baby

(the way I see it, the argument with Fenris wouldn't be any worse than their usual banter, but in this case it happened after a long shitty day for Anders, and it was simply the last straw (hah), not because Fenris said something unforgivable)

http://dragonage-kink.livejournal.com/15999.html?thread=61896319#t61896319