Interesting article. There was an something on the BBC News website a while back with two sides of a similar argument, only one side was written in a style that was supposed to be easier to read; it certainly wasn't for me as it was written with a more southern (southern English that is) accent and I had to re-read certain words several times to work out what they were supposed to be. I know this part was only covere…
The letter thorn (þ), when hand-written, looks a lot like the letter Y [1]. So it remains, somewhat, in stuff like "Ye Olde Shoppe." Wikipedia claims that eth and thorn died out in common use (in English, anyway) between 1300 and 1500. Notes: 1 - It gets drawn in one motion, down to the center from the upper left, then looping up to the upper right, back down to the center and down from there. So it looks like a slop…
I suppose a similar thing happened with yogh (ȝ) - instead of being replaced with something less ambiguous it became z in some cases, but is still pronounced the original way. I think it only survives in some Scottish names in that form though.