But Vipper suggested to reduce damage vs structures, not to disable ground targeting in FOW?
Regarding what Vipper said, I technically agree with him, although I doubt it would be good to indirectly buff defensive structures again at this point.
As a side note to the FOW shooting: I'd rather had it gone too. Yes, it allows good players to get some extra performance out of a unit, but even with all suspension of disbelief possible I always find it weird that units are able to do a pin point shot at something they have absolutely no line of sight on. It also really diminishes the value of smoke. Removing that mechanic would take away from micro focus, but put more emphasis on positioning and defense in depth.
I said that I disagree with the change proposed (with reference to the change that Vipper suggested), I did not say anything about disabling it. I am not sure where you got disabling from.
Because if suddenly there's damage reduction for shooting in the FOW for one unit, every other unit should have something similar too. Otherwise, there's a weird rule that only applies to one unit. And as you said, it'd be a buff to defensive buildings; the change would be similar to a straight HP buff ...
Smoke could disable any targeting reticle, but that's like changing major parts of the play mechanic.