This is ridiculous. And to have no way to turn it off or assign it to a different (Out of the way and unused) button is a horrendous flaw by both the damage it can do and how absurdly easy it would be to fix. I am peeved and extremely disappointed in Opera for allowing this to be a problem for years and causing me to lose over an hour of painstaking, creative work that I can't get back.

Either fix it, change it, or forward this message to somebody who can. Absolutely idiotic that this is still an issue. I don't care about your excuses or reasons for it existing or "countermeasures" that require a secondary key press so it doesn't activate (Which requires the Alt key to be intentionally pressed in the first place), just fix this glaring mistake of a "feature" or continue losing users over it, myself included.