This is quite helpful.

I think it'd be worth explicitly noting that using any of the mutating methods (append, delete, set, or sort) will change the URL to contain the application/x-www-form-urlencoded-encoded characters. And perhaps including one of the shorter examples of such mutations from #491, such as

const url = new URL('http://httpbin.org/anything?a=b ~');

console.log(url.href);   // "http://httpbin.org/anything?a=b%20~"
url.searchParams.sort();
console.log(url.href);   // "http://httpbin.org/anything?a=b+%7E"

And including one of the reading examples would be good too, such as

const url = new URL('http://httpbin.org/anything?a=~&b=%7E');
console.log(url.search); // "?a=~&b=%7E"

// Both "~"
console.log(url.searchParams.get('a'));
console.log(url.searchParams.get('b'));

LGTM. We should update our stylesheet to not italicize pre blocks inside of notes, I think.