What the hell?? If MY underwear talked they'd be going into the incinerator pretty much immediately.
I never understand this "you don't notice, but others do!" business. When I'm getting a little rank, I SMELL IT. When my clothes are musty, I smell that, too! (In fact, I'm often concerned about mustiness when others assure me up and down they can't smell anything off about some piece of clothing I'm wearing or thinking of wearing.) Although considering ppl I've known who've had serious BO or really dusty, old-smelling clothes and not seemed to realize it...

It's known as olfactory adaptation. The body releases chemicals to help neutralize odors that you are frequently exposed to. So if you regularly wear too much perfume, or you live near a factory or something, you become desensitized to the smell.
I'm familiar w/the concept and I have experienced it. (Esp. that living near a factory business - whenever I go to visit my parents, I'm shocked by the strength of the smell from the paper plant, b/c while it surely stank when I was a kid, it just never seemed that STRONG.) But even so I always seem to be even more sensitive to my own scent than anyone around me. (Then again, I also always seem to be more sensitive to everyone else's scent than they are, too.)
3 pints a day?! *googles* Holy crap, it's true. Why didn't my underwear ever TELL me?!!
I remember reading something once, from wartime or post wartime days, where it was pointed out that American girls always looked so bandbox fresh because they, freakishly, wore clean underpants and washed daily. A lady I knew who was a young woman in WWII in England told me frankly that it never even OCCURRED to girls to change their underpants more than once a week when she was a teen.
"Ew, I'm, like, gonna tell everyone that Dot stinks."

"Yeah, she should, like, wash us in Lux. She would be so much more fetch."

"Garter, stop trying to make 'fetch' happen! 'Fetch' is never going to happen!"
What? Where did this ad run? ...a little racy/humiliating for 1942.
If your underwear starts talking to you or to anyone else, it is definitely time to wash clothes... and call your therapist.
It's like some horrible Twilight Zone episode with sentient conniving underpants!