I think it's pretty common. As concrete sources, Eric Raymond's edition of the jargon file not only bothers to cover dress in quite some detail, but is pretty insistent what it includes as well as excludes:
Certainly for me, that entire section of his website (and also his hacker-howto.html) was something that I took seriously when I was in grade school and first learning about hacker culture. Even today I doubt there are things on the web with better claims to defining and documenting the hacker stereotype as Eric Raymond's writings.
http://www.catb.org/~esr/jargon/html/dress.html
Certainly for me, that entire section of his website (and also his hacker-howto.html) was something that I took seriously when I was in grade school and first learning about hacker culture. Even today I doubt there are things on the web with better claims to defining and documenting the hacker stereotype as Eric Raymond's writings.