It really depends on the dealer and how you handle the situation.
They are, for the most part, human after all. ^_-

I have rather limited knowledge on most shows, I'm definitely 
no otaku, so I usually don't feel secure enough in pointing out what
seems like an error to me. Make sure you're correct before you do so.

I have corrected a couple of widely-used dealers when I was sure
there was a mistake and, in each case, was thanked for the help and
saw a quick correction take place. I've also pointed out a mistake
at a small dealer who thanked me but left the mistake in place....