[coldtea]

I'd say both sets.

Hardly any of my colleagues knows what POSIX is (and surely not in any depth, even those that do), but they still SSH and use editors that include Vim all the time...

I'd say in a company of 50+ SSHing people, around 5-6 know POSIX and its history, and usually the older ones (35+).

[unveres]

I think it's better to expect more from a specialist than less. ;)