* What led up to the situation?

     Checking for defects with

[test-][gn]roff -mandoc -t -K utf8 -rF0 -rHY=0 -ww -b -z < "man page"

  [test-groff is a script in the repository for "groff"] (local copy and
"troff" slightly changed by me).

   * What was the outcome of this action?

troff: backtrace: file 'stdin':708
troff:stdin:708: warning: macro '..``' not defined
troff: backtrace: file 'stdin':953
troff:stdin:953: warning: trailing space in the line


   * What outcome did you expect instead?

     No output (no warnings).

-.-

  General remarks and further material, if a diff-file exist, are in the
attachments.