Guys, the whole issue is being blown totally out of proportion.
Cloud flying in gliders was common in the 50's & early 60's because:-
A lot of the pilots were WWII RAF trained and could even do spin recovery on instruments. Alternatively the pilots could teach themselves cloud flying because of the aircraft factors below (See Peter Scott's book "Eye of the Wind" if you don't believe it)
The old wooden gliders had totally speed limiting airbrakes - they won't go past VNE even in a vertical dive
Even without the brakes the old wooden gliders took a long time to accelerate to VNE because of the built in drag.
The amount of wind noise generated is a very clear indication to the pilot that something nasty is developing.
The old wooden gliders needed a lot of height to do decent distances.
Their performance didn't alter that much if they collected a bit of ice in the process.
Wave wasn't widely known about, Scotland was far away and height diplomas had to be done in clouds.
With glass gliders these days very little of the above applies.
Airbrakes are only speed limiting to about 45 degrees dive angle
They accelerate very quickly and are very quiet at all speeds
Performance goes to worms with dead insects stuck to the wings, never mind ice.
So while technically gliders can fly in cloud, only an extremely small number of pilots these day choose to do so, and normally very infrequently.
"Don't panic, Captain Mainwaring"