Alessandro,
I just made this correction on my site.
First off, I use NotePad ++ as my editor. This allows me the option to save a file with encoding of UTF-8.
Open wxsim.js, then set encoding to UTF-8. I found 5 instances of the degree symbol in wxsim.js. The first is on line 121 in my wxsim.js and is
var temptitle = "