This being Friday the 13th, I thought I'd ask about superstitions and taboos in your campaign settings. Do you have them and, if so, do they have any consequences for being flouted?
In my old AD&D games, I took seriously the implications of the Monster Manual and Dungeon Masters Guide about attracting the attention of demons and devils by speaking their names aloud and so the players quickly learned never to refer to them by name (which is why I was intrigued by this old urban legend). In other games, such my old Traveller campaign, ignoring a taboo resulted in negative reactions among the locals (such as dressing in a "mourning color" on one planet).
Did anyone else ever do stuff like this in their campaigns?