I can smell the nerd from the first comment, which uses characters to distinguish differing pronounciations of "th". Is that a peccadillo of his own, or is it a thing?
http://thedutras.blogspot.com/
When did English drop those letters? 400 years ago? If he really wants to use those letters, he should also use the grammar and vocabulary constructs.
http://www.gutenberg.org/cache/epub/8102/pg8102.html
(all that being said, I would mind a few more letters to use in English, particularly the schwa http://en.wikipedia.org/wiki/Schwa would make everybody's life easier w/r to spelling).