Sorry, hit the post button early and was shortly thereafter called away.
Basically, I've got a more-or-less vanilla install on Raspbian Stretch and lighttpd was configured with mod_compress by default. This default (maybe not the fact that this module was enabled, but also the way it was configured) breaks the Query Log page of the web interface.
When I comment out mod_compress, the Query Log page displays log info. With the module active, it displays an error in the Dev Tools console: ERR_CONTENT_DECODING_FAILED and does not display any logging data.
I downloaded a copy of the queries.js file from the repo (AdminLTE/queries.js at master · pi-hole/AdminLTE · GitHub), diff'd it with what was on the server, and then patched the file on the server. Now the page loads fine, with compression enabled for javascript.
But the only difference that was shown between the two is in the leading comment:
root@pibox:/var/www/html/admin/scripts/pi-hole/js# diff -a queries.js queries.js.bkup
1c1,2
< /* 2017 Pi-hole, LLC (https://pi-hole.net)
---
> /* Pi-hole: A black hole for Internet advertisements
> * (c) 2017 Pi-hole, LLC (https://pi-hole.net)