When I posted this idea on the email list (http://lists.gnu.org/r/groff/2024-01/msg00119.html), Branden had some implementation concerns (http://lists.gnu.org/r/groff/2024-02/msg00014.html), but no one shot down the concept, so I submit it here to be formally accepted or rejected.

Having no-space mode suppress .bp seems quirky, and at odds with the info manual's stated use case for the mode: "A paragraphing macro might ordinarily insert vertical space to separate paragraphs.  A section heading macro could invoke 'ns' to suppress this spacing for the first paragraph in a section."  (CSTR #54, befitting its terser nature, suggests no usage for .ns.)

Of course this long-historical behavior cannot be overturned.  However, two ideas were floated in the email thread to get the sometimes-desired "no-space mode that honors bp" (which hopefully someone will coin a less clunky name for):

• .ns currently takes no arguments -- but it could, a value to specify "suppress only vertical space, but not page breaks."  The behavior with no argument would be unchanged, so historical usage would work as it always has.
• There could be a new, alternate no-space-mode request, perhaps named .ns1.

A real-world problem this can solve is the -ms package's handling of vertical space after displays; see earlier posts in the first email-list thread cited above.