Whenever the lenses on mine have fogged up, I haven't been able to see the dot at all. If the back side of the lens is fogged (the surface that reflects the dot to your eye), it's not the same as just taping up the front of the optic.
Fog has rarely been a problem for my RMRs though except when doing it on purpose.
Last edited by Yondering; 01/12/19.
