> The browser can't actually play sound unless 1) it's triggered as the result of a user action (such as a mouse click) or 2) if you've often listened to sound on that page in the past.

The point is that a click should not give the website permission to play audio - that should be handled much explicitly and not just the user selecting text or some other interaction. Besides, last time I checked Firefox still let AudioContext play sound without any user interaction even though the <audio> element has more restrictions. Which is another problem: the HTML + JS spec is too bloated to properly secure things.