I'll add a new observation that comes from some googling.
As I mentioned before, the 2006 Aprilia SR50 Ditech, a sporty moped, has the same basic dashboard as the Griso (and some others). It differs from the Griso in that it doesn't have an air pressure sensor on its PCB (as can be seen in a photo). The SR50 dash's case, however, is the same one used for the Griso, including the two small ports or air vents, even though it doesn't need them for a sensor. These ports were reported to be open, not sealed, by apriliaforum.com user Techrat1. (And the new replacement dashes for the SR50 have the new, single large port that jlburgess revealed above.)
What surprises me is that I can find absolutely no mentions of a fogging or moisture problem with this SR50 dashboard when I google. Since it has the same vents I would expect it to have the same problem. I would expect it to allow the same entry of water vapor on humid days, with condensation showing on cold sunny ones.
What does this mean for us? All I can conclude is that better protection of the dashboard from external water and mist might help, since the SR50 does have better protection, like this:
(http://thumb.ibb.co/cTg1x7/2006_on_Aprilia_RS50.png) (http://ibb.co/cTg1x7)
This conclusion goes contrary to my previously-maintained position that the problem is likely coming from condensing water vapor (not from intrusion of liquid water, as in a mist). But if my previous belief were correct, I don't see why the SR50 dash would have no reports of a fogging/moisture problem on the web.
I don't know about the protection of the same dash on the 2006 Tuono or the 2006 Pegaso 650, or even the Guzzi Stelvio. They all fog. Whether there is enough difference between their shielding and the RS50's to explain the apparent lack of fogging in the latter, I can't say.
Some of you have previously suggested that water or mist intrusion is the problem, and it has been suggested that using a fairing, no matter how small, helps. (I've agreed with that.) I don't see how else to explain the SR50 experience. <sigh>
Conformal coatings, desiccating breathers, and slack diaphragms may be beside the point with better protection. It's hard to say for sure. How a Griso would look with enough protection to alleviate the problem completely is another issue.
My data are also dicey. My inability to find references to fogging problems in the SR50 doesn't prove there aren't any.
Moto
P.S. The key photos of the SR50 case and PCB, by Techrat1, are found here:
http://www.apriliaforum.com/forums/showthread.php?180601-Digi-Dash-modding-or-repair/page2 (http://www.apriliaforum.com/forums/showthread.php?180601-Digi-Dash-modding-or-repair/page2)