[cuddlybacon]

It is also signals a package of personality traits:

* rejecting other personal hygiene customs

* being noticeably more pedantic

* picking every battle/argument

* lower than normal respect for other's boundaries

* lower than normal awareness of how their actions effect others

* making "being rational" a core part of their identity

* dismissing human behaviors they don't do as irrational. usually these are the ones where rational explanations do exist, they are just difficult to re-invent on the spot.

This package is common enough to have earned itself a name, which happens to be the easiest visual indicator.