OK.

> s/GUILE/Guile/ and two spaces after and end-of-sentence period.

How so? Two trailing spaces after the period or two newlines?
Is there a style guide somewhere? I was mainly copying and pasting
from srfi-modules.texi.

> I’d rather call it ‘set-record-type-printer!’ (it prints records, but
> it’s the printer of the record type).  What do you think?
>
> You could add a docstring here.
>
> And don’t forget to add srfi-9/gnu.scm to ‘SRFI_SOURCES’ in
> modules/Makefile.am.

Done.