1) editorial: In numeric/comma, for "commma-rule" read "comma-rule".
Fixed.
2) There is no formatter to force exponential notation output corresponding to ~E in Common Lisp, %e/%E in C, and Fortran D, E, and F. I suggest numeric/float. The following 4 additional parameters would be needed:
One could be written portably, and I'm already fighting feature creep.
3) numeric/si: allow only 1024 or 1000 as bases, as the other bases are just unintelligible. Better yet, change to a boolean variable.
Alternately, a state variable or extra param for the abbreviations could allow CJK rounding by 10,000: 万、億、兆、etc.
4) fl: what happens when the line position is not known, as when the last output was via an R7RS-small output procedure?
Added clarification that row always starts at 0, and output to the port prior to or outside show gives undefined behavior.
5) nothing: this name conflicts with my forthcoming Maybe/Either SRFI: I suggest changing it to "silence" even though this is a breaking change with SRFI 159.
Alternately "blank" but that sounds like whitespace. I'm fine with "silence" if no objections.
6) editorial: Need a blank line above joined/last.
Added.
7) Pretty printing: specify Emacs compatibility, or else deviations from it.
Too big a can of worms :)