Case insensitivity by default is getting to be rare these days. Of my 40 implementations, only MIT, Scheme48 (but not scsh), SISC, SCM, STklos, TinyScheme, Scheme 9, Dream, XLISP, Elk, UMB, VX, Oaklisp reply #t to (eq? 't 'T).
Arthur says: 13/40 is not rare. It's almost a third.
John says: Okay, but between you and me and the bedpost, the only ones that count for much nowadays are the first four, five, or six, depending.
Arthur says: But how many of the case-sensitive implementations count for much? If we're to compute a ratio, we need a comparable numerator and denominator.