Is it impossible to combat electric guitar buzz when playing moderately hard, without adding excessive bow and setting a ridiculously high action?
No, but thicker strings help.
If you can hear the buzz through the amp, then you have a problem with the action on your guitar, and you should get it set up (either by yourself or by a professional). If the buzz is only acoustic and the buzz doesn't go through the pickups, then there's no point changing anything. You could raise the action, but then you'd be doing just that: raising the action. You'll find that many high end guitars, such as those by Fender and Gibson (just to name some examples, I know there are others) have that fret buzz, but it doesn't really matter because they're electric guitars and the buzz is only acoustic.