OK, but I think it is symmetrical. That is, if you breathe out a virus then someone else will be able to breathe it in regardless of mask wearing.

If you breathe out an infected droplet while wearing a mask then it most likely will not get past the mask. however, if you were not wearing a mask then another mask wearer would not be able to breate in the droplet through his mask anyway.

Also, if someone does get a droplet with a virus stuck to their mask, what is the guarantee that the virus will remain on the mask and not enter your body? If it does remain on the mask, shouldn't we be extremely careful how we dispose of all masks?