Let's exclude the elderly, too. Once you get to a certain age, you really don't care what anyone thinks, which is really a blessing anyway. They aren't trying as hard to hide it.
Since I often wear Real Fit in public and sometimes something all the way up to Northshore Supremes, I'm constantly evaluating other people to see if I can spot a diaper. This is partly because the Real Fit is only good for buying me time to get to a bathroom and I want to be more comfortable wearing real diapers. It's very difficult to spot a concealed diaper. Even on people that I see regularly that I'm convinced are wearing it's difficult to be sure. I want to be able to look at myself the same way but of course you can't. And I can't ask anyone what kind of diaper they are wearing so I can compare to what I think they are wearing. But this is why I'm with the opinion that nobody will notice your diaper unless they wear them themselves. The average person doesn't have the programming in their brain to even consider that you might have a diaper in your pants. I know what I'm looking for and unless it's blatant, I can't tell.
For it to be obvious, they would have to be wearing thin or see thru pants, or tight jeans, or have too many stuffers, or be carrying 80 ounces of urine, etc.
But, all that said, I'm human and I haven't quite shaken the self-conscious aspect of it.