I didn't actually watch the speech, but something that caught my attention from the pics I have seen of it is the gloves of the Marine to Biden's right are in a spotlight. It also appears that he is further to the right than the Marine to Biden's left is to the left, judging by the building behind them, but that may just be the angle of the pictures I have looked at. I would expect them to have been positioned so as to evenly bracket Biden.
Don't know that it means anything but if the Marine was intentionally standing so as to spotlight his white gloves it could be comms of some sort. It just caught my attention.