On Sun, Sep 12, 2021 at 04:56:21PM +0200, Alejandro Colomar (man-pages) wrote:

I'm a bit worried that this might be overcomplicating it, and maybe a
hypothetical .SSS macro would be useful here (or another solution).  Do you
have any thoughts about it?

That hypothetical macro would behave like .TP + .B + .RS (as shown above;
and that .RS would only end at a following .SSS/.SS/.SH)

It is not important to me that my .SSS macro be used, but for reference
here it is:

.de1 SSS
.  if !r SSS_SN_ORIG .nr SSS_SN_ORIG \\n[SN]
.  nr SN (2 * \\n[SSS_SN_ORIG])
.  SS \&\\$*
.  nr SN (\\n[SSS_SN_ORIG])
..