@benjykid said in Opera empties the FEATURE_BROWSER_EMULATION registry key on updates/reinstall:

I have no idea what browser_assistant.exe is good for. But it it is in the run registry key, so it runs at startup.

If you have no idea, then likely you could remove it from run key (and from task scheduler and other places; I personally deleted entire opera assistant folder too).

I'm getting bug reports that websites in my application are not displaying correctly. And then I find that this registry key got deleted.

You could just re-insert your required key at start of your application. We once considered that, but fortunately our app (or rather rarely used part of it) could work with older IE compatibility level and thereby we have no direct experience with it.