On 11/23/24 18:17, Paul Eggert wrote:
> that's a recently-introduced groff bug. I reported it here:
> 
> https://savannah.gnu.org/bugs/index.php?66481

 From the followup to that groff bug report, it appears that the groff 
maintainers don't consider this to be a bug, though they do say it is a 
compatibility issue. To work around this for grep, I installed the first 
attached patch. I noticed some other glitches too (some with traditional 
troff) and installed the second attached patch while I was in the 
neighborhood.

Closing the bug report. Thanks again for reporting the issue.