I think the Character/You fic kicked off again in MCU fandom. Or, at least that's where I started seeing a lot of it again, specifically Loki/You, though some Bucky/You more recently.

Like you (specifically you), I had always thought it was one of those huge 'don't's for writing, unless you (general you) were trying to be artistic, and generally knew what you (ditto) were doing.