I opened an issue [1] for this on CL gitlab, then saw the mailing list info.

At any rate, I was a little confused by how the :parenscript readtable behaves with ACL mlisp (case-sensitive-lower). It wasn't obvious to me at first, but I found a place in the utility function encode-js-identifier that swaps case for all-lowercase and all-uppercase symbols. Changing the readtable definition and disabling that case-swapping code (for allegro only) kept the intended behavior. Alternatively, you can use (excl:in-case-mode :common), but that's not very fun. See the gitlab issue for details, linked below.

Fiddly, but maybe this will save someone a few minutes one day.

-Sky

[1] https://gitlab.common-lisp.net/parenscript/parenscript/issues/1