If we could stamp out rudeness, I agree the world would be a much better place. I'm sorry people are acting like this.
Mis-reading descriptions:
Ask them to look again, and then don't bother explaining to them further, or just tell them to take it up with a Magi. But also re-read the description yourself and think about tightening it up. Sometimes you fiddle with a description and things get dropped, or become much less clear than they were before, or maybe it wasn't as clear as you thought it was in the first place.
"Modern" clothing in the fantasy rooms:
Bah. "Denim" is a cloth "de Nimes" from Nimes in France. "Jeans" are in the style of Genoa. Cotton was all over the Mediterranean countries. Twill-weave cotton fustian pants are perfectly fine late medieval wear, though, okay, not the five-pocket style with copper rivets and a designer label leather patch on the back.

But to come down to it, what matters is "appropriate to the setting" when it breaks the setting for others. No pulling out your cell phone in the tavern even if your char admits there's no signal. As someone who does Rennfaire type stuff, I kinda wince at the number of thigh-high skirts and halter bikinis in the tavern: in a real medieval setting, you'd only see that much flesh inside a brothel. So if someone comments on that sort of thing in-char, that's reasonable and not harassing your char. But blue pants and laced low white shoes shouldn't be grounds for harassing you in PMs. (Of course, people may still validly assume you're being sloppy about taking chars from TMP to other rooms, or that you don't know enough to figure out what is medieval style clothing. They just shouldn't be rude to you about it.)