DON’T become even a casual nerd about historical fashion because you’ll start looking at pseudo-medieval fantasy and going “that jacket and those breeches are 200 years apart and reflect extremely different social movements” and “oh no they were NOT making shirts like that prior to industrialization” and “a fly front? in MY ~1500s???”
The thing about this is that it's not even deliberate. People often respond with deep offense that you're not taking into consideration that it's fantasy, but it's not really a choice: when you understand a topic well enough, these issues are immediately apparent and immersion-breaking in much the same way something more obvious would jump out at a normal person.
It's like if there were suddenly an 18th century style revolver in Westeros, but no other use of gunpowder. Or a Model T Ford. It would stand out and make you go "how did this get here?" even if you understood that this is fantasy!
