"Is ___[fill in the blank]___ a sin?"
Who are these posters? Did any of these people go to catechism class?
Trolls I would suspect.
Not everyone is a cradle/longtime trad. There are lots of isolated folks out there who rely on CathInfo as a sort of free correspondence course since the lifeboat Church doesn't exactly have neighborhood equivalents to RCIA. With reverts, what little they remember was bogus ordo catechism. Even the faithful with their regularly claimed pews might get stumped on the finer points of moral theology manuals.
Should they at least make an attempt to use the search function and try to educate themselves without being newbie nuisances (phrasing this as one myself for a while)? Yes, they should. Should we dismiss them as newbie nuisances? Maybe, maybe not. Case by case.