It's onepostaccount. Mistakenly cleansed chrome cookies while cleaning registry entries of Opera before I re-install it again. So sign-in info was gone, I forgot PW and my temp-mail was gone too, hihi.
Anyways, I had a stroke of luck to pinpoint the problem really fast so I decided to write back real quick:
opera:config#UserPrefs|EnableHardwareAcceleration was set to 1
Default value is 0. 32 or 64 bit, doesn't matter (link works in both versions now). Somewhere down the line I changed it for a good reason. Why it backfired now, on this reddit post that looks the same as any other I have seen... I don't have any illusion of ever finding out.
What I know is: laptop I use has shitty OEM drivers which I have no easy way of updating (switchable intel+amd graphic). Coupling that with, from what I remember, not so good Opera 12 support for HW acceleration, this problem could be unique to my case.
I'll keep my eyes peeled on this topic for about a week if anything comes up, but for now that's all folks.
Perhaps a Mod can add [solved] tag to the title cause I locked myself out from previous account.