Doh. The config section I was using in fact
wasn't correct, but once I fixed it, the styletags once again work.
First, for no particularly good reason, I commented out the
ns_param adp ".adp"
line just to see what would happen. The styletags worked.
However, this seemed bizarre so I looked again at the relevant section in the canonical reference at AOLServer.com (http://aolserver.com/docs/admin/config-reference.tcl.txt) where both ns_params in this section are indeed included, neither one commented out.
And then I noticed that the order I listed them in my config file was reversed from the order they list--and in fact was reversed from what I posted above (must have copied&pasted that from the reference and not from my actual nsd file). Switching them and leaving them both enabled results in a correctly performing system.
So, the correct section is as above:
#
# ADP custom parsers -- see adp.c
#
ns_section "ns/server/${servername}/adp/parsers"
ns_param adp ".adp" ;# The simple parser looks for <% ... %>
ns_param fancy ".adp" ;# The fancy parser does a lot more.
Seems like perhaps there should be a big fat warning in AOLServer's reference "Don't switch the order of these params!!" One wouldn't presume that it would make a difference, and one careless slip while editing can induce a long bout of head-scratching. Well, the scabs will heal.