It is not possible to gauge intelligence or academic credential by visual inspection, unless someone is wearing an academic gown. Some very accomplished people positively seem to enjoy looking disheveled.
Can confirm. A friend of mine has been consulting now for over 15 years. He's an excellent engineer with some valuable specialization. Met him after work for dinner and he shows up in crappy jeans and sandals. "Why are you dressed like that, didn't you just come from a client site?" "It's part of the uniform." Apparently IDGAF is a signal in more ways than I thought. In this case it shows that you are good enough not to need to conform - and he's right. I do wonder weather dressing better but finding another way to signal value might take him up a notch, but I honestly couldn't say.
And the aforementioned (and appropriately flagged) comment isn't about people looking shabby, it's about people looking Hispanic or South Asian. No one questions whether a white person in casual dress might be an engineer, scientist or something other than a janitor.
Having a strict dress code isn't a sign of status in my book.
When I was in college there was a direct correlation between brilliance and how disheveled one looked.