When I put two voices on the same staff that have identical markings for dynamics and tempo, Lilypond prints them both, one above the other. Looking in the archives the other day I saw that the approved solution is to pull these markings out and attach them to another voice that is all spaces. Now I can't find those postings. They were from 2003 as I remember. Do we have multiple archives of the mailing list? Or maybe I should just go check myself into a nursing home. :(
Back to my original question: if Lilypond can see that one of these things needs to be moved, how hard would it be to have it determine that they are identical and just not print one of them?
I don't even know whether this is a request for a new feature or for a pointer to an existing one.