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.