403 is per request, not requester. I get random 403s when just browsing some websites. Does that mean I should close the browser and not hit refresh for fear of breaking some wire fraud unauthorized access law?

If you go by the semantics of what the 403 code means, absolutely, that's excatly what the status code means.

In practice there's of course nuance, like anyone will occasionally type in the wrong password on a log-in screen, maybe try again and then realize it was the wrong log-in prompt. That's mostly fine.

That's different from deliberate trying to circumvent a measure like this. If you are doing the stuff in the link, you are absolutely crossing a line and you know it.

There's a large difference between "I got a 403 so I hit F5 once" and "I got a 403 so I used a residential proxy and spoofed my user-agent".

I thought the semantics of 403 was "look for the actual semantics in the response body".