Worse, due to the aforementioned permissive error handling in HTML parsers, a closing </br> tag will end up inserting a second line break

You close them in the same tag:

    <br/>

Wrong.[1]

> if the element is one of the void elements, or if the element is a foreign element, then there may be a single U+002F SOLIDUS character (/)

If you're going to be pedantic, at least be correct about it.

[1]: https://html.spec.whatwg.org/multipage/syntax.html#start-tag...