ELU tends to dismiss as general reference questions that are common knowledge in anglophone countries, but definitely hard or nearly impossible to look up. This is pretty obvious - expressions based on baseball are the very blood of every american, meanwhile "reaching the home plate" draws a blank from a foreigner - and while they may look up the rules of baseball, and find out what that means in the end, understanding the idiomatic expression in case of dating shouldn't require knowing the rules of the sport.
Idioms that are simultaneously brand names. Idiomatic expressions that mutate wildly, with a core too short to look up. Complex phrasal verbs (parsing a cluster of two or three phrasal verbs using a dictionary is hard if you don't know where one ends and the other begins) Common misspellings. Common Pop-culture references that sound like outlandish idioms. Metaphors based on national culture. They all should deserve a chance on ELL, while ELU will find them annoying, uninteresting, worthless and "general reference".
Personally, I suggest to precisely limit the list of sites which are "General Reference":
Questions not answered by a simple look-up to these three resources shouldn't be considered general reference. Questions that ask further explanation of dictionary definition (these are often too brief and sometimes circular) are not general reference. Questions asking the difference between two not obviously different synonyms are not general reference either.