hello Ingo, thanks for this detailed anwser.
> The reason i'm sticking to groff is that groff has been the typesetter > predominantly used by BSD systems during the last 25 years, that i think everyone else have good reasons to be stuck on its own prefered implementation. > I think it's a general phenomenon that you can't have full unification > among Free Software projects. The best you can usually get is some > cooperation to improve compatibility. indeed. regards Marc