I don't know if this is an oversight or what, but my female character was walking around New Ark Slums naked from the waist up, and no one seemed to care. "Hey, there's this hot babe showing off her great rack and lactating....just another day in the slums!" Is the indecent tag used just for named NPCs like Fawn? Fawn will react if you aren't dressed properly, but pretty much everyone in the slums didn't bat an eye when my character was indecent.
Yeah, only named NPCs will react. Anywhere that's not UNA, it might be a little weird, but it isn't socially unacceptable to be nude/exposed.
As well, I try to make non-named NPC dialogue at least entertaining, and there's only so many ways I can write 'Hey, nice rack!' if they all were to have dialogue for the player looking indecent.