Well, there's the "mirrors and copulation are abominable, because they increase the number of men" angle ... (Borges, of course: https://en.wikipedia.org/wiki/

Well, there's the "mirrors and copulation are abominable, because they increase the number of men" angle ... (Borges, of course: https://en.wikipedia.org/wiki/Tlön,_Uqbar,_Orbis_Tertius https://en.wikipedia.org/wiki/Tlön,_Uqbar,_Orbis_Tertius , probably piling on the known historical puritan dislike of mirrors because of sinful vanity.)