Thanks to everyone who responded.  Based on the collected
information, i've cobbled together a runtime check for
‘sql-quote’.  It and some tests are in the attached program.
To play:

 guile -s normalize.scm
 guile -s normalize.scm stupid

The code assumes Guile 2 DTRT, but if you have doubts, you can

 sed -i 's/guile-2/&-not-really/' normalize.scm

to disable that assumption.  In any case, the program should exit
successfully, indicating smooth ‘write’ / ‘read’ round-tripping.
This is so (both w/ and w/o "stupid") for Guile 1.4.1.124 and 1.8.7.

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