I like the idea, but I’m annoyed by the inconsistency.

The þ is the th sound in “both”, but not the th sound in “the”; that’s a ð.

Ðough, ðat, ðere

Þorough, boþ, þree

Dude, if you’re going to do this, you should really be spelling ‘that’ like ðat.

Why?

This is exactly it. It has always been up to the browser to decide how to render a website. There have always been differences. The idea that a browser can honour or ignore parts of the content has always been part of it.

If anything should be illegal, it should be websites 's constant attempts to bypass user preferences. Some of that shit is plain malware.