in my 20-year stretch as a dl, i've worn in dozens of situations, from under shorts in middle school to 12-hour work shifts in an insulated suit. no problems here!
people probably won't notice unless you make it obvious. if it's noticed, people probably won't care unless you make it awkward. if it's awkward, people probably won't remember you for it unless they know you already. if they remember, they still won't know why you choose to wear your peculiar choice of underpants unless you choose to tell them. :-)