In his free time, Anderson is a superhero (I'm thinking a Superman analogue, but whatever floats your boat), which naturally makes him sleep-deprived and distracted, and maybe it's hard for him to tell what humans can and can't see/notice. Sherlock knows he's a superhero, but doesn't see that as an excuse or even a reason for his behavior. He doesn't say anything about it because it's so obvious that it's boring--Anderson doesn't even wear a mask, for crying out loud! ...Nobody else realizes that Anderson's the superhero.