I often visit US card stores before Regionals and this is by FAR what grinds my gears more than anything, especially when the have a display case away from the main desk and you can’t look at conditions quickly.
Only time this kinda works is the one store used TCGplayer lows as a rough price guide, I could find the prices easily.
Stores/vendors knowingly selling fake cards.
Besides it surely being illegal (right?), it leaves a bad taste to have real cards and fakes in the same store/vendor, even if they are in different sections of a display cabinet.
I think the situation you encountered at the last card shop where the employees identified you two as picky customers that are solely looking to make money from them, has parallels to me ignoring messages on eBay from buyers asking ‘does this card have any scratches or white spots etc’.
It’s just physical vs online. The physical experience of being ignored or shunned is likely more jarring though.
I wasn’t even aware that card shops can still carry gradeable cards. I always just assume that they cherry-pick the best condition ones to send to PSA themselves and sell off anything with imperfections raw. At least for vintage, maybe they overlook modern ones more often.
Charging NM prices for every card condition.
I almost had a heart attack as my LGS for decades has been “Game Empire”. I wish their shop keeps were more knowledgeable about more things, BUT they have at least one specialist for each franchise they sell, so it’s not bad.
My pet peeve happened several years ago, when I wanted to try getting into organized play again. I did not understand the terms for the play session, and when I asked again later, the shopkeep was noticeably annoyed. Now, I’m an unassuming person, and figured he’d just had a bad morning, but when a business treats customers like they should know better, that’s always my biggest pet peeve.
As far as Red flags, if a store has lots of things all mixed together, like vintage stuff with modern and some legacy, and promos mixed in with standard sets… Ugh. 