I feel that the two snape's in the two realities are actually rather similar. they share most memories and experiences, it seems as if only after harry's fifth year in hogwarts one reality splits from the other. severus sacrifices himself in a reality where the dark lord has already won and where dumbledore and harry are dead. that must have taken at least as much courage and selflessness as the snape in the canon realits has shown! I loved the appearances of teddy and albus severus in the story. it is written very atmospherically, especially the abyss.