Stating that one "lost" to another one's post, regardless of whether or not it's in a "You X, You Lose" thread, has merely become a colloquialism for one's initial reaction to said post.
Why does that sound like something I might say?
The funny thing, we don't bother to elaborate on how we lost, and we give the topic title as abbreviations like YFOYL. Eventually we'll have so many of those topics that an acronym could refer to any of them, and we still won't be any better off. So I've quickly been interpreting "I lost" to mean "I had whatever experience you would likely have upon seeing/watching this thing". You can usually tell upon looking at the thing whether it's of disgust, fright, amazement, laughter, or whatever. Except when it could be any of them. Then you still don't know.
^ I lightly lost.
Then you see things like this, and you know even less (it's from the You Laugh You Lose thread).