In regards to the Sprite-High-Five being a plot hole, people have pointed out that every visual instance of people touching sprites (said high five and GrubMom comforting Kanaya) has been the player and their respective sprite. It would make sense that players would be restricted from prototyping themselves in their own sprite, cause that would be a pretty easy mistake to make. All theory obviously, but fairly sound reasoning.

“It would make sense that players would be restricted from prototyping themselves in their own sprite”

Davesprite, Jadesprite, Aradiasprite