Over time, I've found myself not as completely thrilled with this application as I thought I would be. The @ looks kind of... heavy, considering that what it's doing is ultimately kind of a "light" pointer.
I go back and forth on it. A light quoted word does seem nice at times:
func [param] [fail "An error which indicates this line"]
func [param] [fail 'param "An error which indicates the callsite"]
func [param] [fail 'param] ; just blame the parameter as being bad at callsite
func [param] [fail] ; just fail. (blame is <skip>pable, reason is <end>able)