I don't know, the period might feel stronger to you because you have already accepted this meaning for text. For others, the comma feels "stronger" in the context of numbers. Partly because they are used to it, but it makes some sense too, because it is larger and has a defined direction. A period is just a little dot and, when written by hand, could easily be mistaken for a random smudge and vice versa an accidental contact of pen to paper could more easily be mistaken for a dot than for a comma.