Ok I know they aren't the same person, but what Momoshiki did in this chapter parallel's Hagaromo's ability to be a "chakra ghost" that travels through time and space. Momoshiki said the reason he could see him still was due to him possessing the Hyuuga and Uzumaki genes, just like how uniting the Uchiha and Senju genes allowed Hagaromo's ghost to be seen. So like Hagaromo, even though his body has been destroyed Momoshiki is now a chakra ghost like Hagaromo and that is how he was able to communicate with Boruto as well as presumably give him the seal on his hand. Im not sure why Momo would share power with Boruto, but it seems to parallel how Hagaromo gave Naruto and Sasuke power though this time there is likely a more sinister motivation.