Board Thread:Theories and Speculation/@comment-31074250-20170318090411/@comment-28445617-20170413024810

I think I have an idea on what's up with Boruto's Mark and Byakugan.

When Hagoromo bestowed Sasuke the Yin Power he asked him to stretch out his prominent arm. Sasuke raised his left arm and Hagoromo gave him the Yin Power, with a cresent symbol appearing on the palm of his left hand. This Yin Power seems to have stimulated the left side of his body and augmented an ability he already had, the Sharigan in his left eye, which evolved into a special Rinnegan. He later lost the Yin Power when he and Naruto sealed Kaguya, but the augmentation effect from the Yin Power on his Sharigan appears to be permanent.

Boruto was given the mark on his right hand by Momoshiki, who, like Hagoromo I mentioned earlier, is also an Otsutsuki. I reckon Momoshiki bestowed some kind of power to Boruto, which we have yet to see, but like the Yin and Yang Power given to Sasuke and Naruto it augmented an ability Boruto already possessed. Well, he didn't awaken the Byakugan yet, but he has all the requirments to do so. That Byakugan-like thing that flickered on and off in his right eye after he got the mark is most likely a special Byakugan. Anyway, that's my guess on what's going on. Concerning Naruto's augmentation from the Yang Power given in his right hand, it evolved his Sage Jutsu into Six Paths Sage Jutsu and since the Sage Jutsu isn't attributed to any one side of the body, unlike the sharigan which works as two separate eyes that are stronger together, there was no dissymmetry.