Citing the authority of "someone on the internet" won't help them at a home game. Using arguments and citations provided by someone on the internet for why RAW says X is, however, often a good way to convince a table that RAW says X if those arguments and citations were good and accurate, or at least compelling. You just aren't going to emphasize the source as some sort of authority.
I would equate good rules answer on a message board to American legal scholarship. It has no legal authority whatsoever, and ideally a lawyer finds court precedents (binding or otherwise) that they can cite and base their case on. But it's still worth consulting and sometimes even citing scholarship for the sake of its arguments or effective summary of something, and for the sake of finding out what the actual authorities you should really be consulting are.