> In the early days of Python, some employers used it as a way to filter for candidates who were ahead of the curve. I believe Paul Graham mentioned Lisp being good for attracting better programmers

Possibly "The Python Paradox" [1] and/or "Beating the Averages" [2]. (The first one, from 2004, is a bit of an odd read nowadays, since it no longer applies to Python.)

[1] http://www.paulgraham.com/pypar.html [2] http://www.paulgraham.com/avg.html