Means "I never liked your smile". A popularmeme among artists, writers and memers, mainly gamers. Originated from the online omori fanbase, hugely popularly among A03 writers.
"yk what? i never liked your smile anyway."
"Huh? You read that fic too?"
"Yeah of the 12 year old asian beat up kid who said INLYS"
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi