Just a few remarks after several years of oceanic and other flying.
Oddly enough, the only other case I have recent knowledge of was an own company A330, over the Atlantic, which had an altitude excursion following,"the worst turbulence the captain had ever experienced".
Oceanic traffic goes in swarms in the same direction with only occasional opposite traffic. If everyone offset it would achieve nothing.
In high density Europe under RVSM it would be reassuring to see the oppos slide down the other side. You have to be there with a joint speed of 1,000 mph to appreciate how little time you have to react to a potential conflict.
With regard to reducing lateral separation on the Atlantic by 50%, consider this: communication is still by antiquated HF via radio operators, not ATC controllers.
On a bad day you may take 20 minutes to make contact with the guy and possibly never get a response to a request to deviate off track due to severe weather.
By then you have probably had to take the initiative to take whatever avoiding action is required.
With reduced lateral separation it would just make that, officially, unauthorised deviation more risky.
You don't have to spend much time over the Ocean to reallise how little actual control there is in the continental sense.
I believe the general public would be amazed.