Thanks go out to Orivej Desh—he pointed out what I overlooked, and the LET-OVER-LAMBDA package now works with full functionality restored in SBCL 1.2.2. I have preserved the
:safe-sbcl feature used for testing the version of SBCL, so that descending into
sb-impl::comma is only enabled for SBCL 1.2.2+.
The updated code should be available in the August release of Quicklisp. If you have a fork or clone, please be certain to pull the latest changes from the master branch.