I know in ZTA, it's in the bylaws that we can't wear the crest but letters have a lot of meaning too, so I believed (along with the rest of my pledge class) that we shouldn't wear them and we actually were upset with other chapters on campus for allowing their NMs to wear them. I also feel very strongly that you shouldn't get those little lettered booty shorts because you're essentially sitting on your letters. Maybe I feel strongly about this since I was Ritual Chair...