I appreciate that you went and asked someone for the clarification that this issue is about the preference being set in a cookie and not in user settings, but this doesn't solve the problem for many of us.

For YEARS, on a weekly and sometimes daily basis, always logged-in, always with preferences set to english, it is infuriating to routinely end up receiving results that conflict with your explicit language settings.

What, concretely, do we have to do to get someone at google to push a change from using cookies to a real user-setting to fix this absurdity?

You said they did it for speed. Giving me completely incorrect results in a language I can't even read 1 millisecond faster than giving me results that I actually care about is a win? This is over-optimization.