Is there a way to sort the fonts based on their appearance so that ones that look alike are listed together? Then I could manually delete them.
I suppose it is just a judgment call on which one to delete
Actually your problem is pretty much solved right now. The program works correctly, but it seems that you only want to see identical .ttf files, right? then write this:
./duplicatefinder /library/fonts | grep ttf
or because you copied your fonts folder to desktop:
./duplicatefinder ~/desktop/fonts | grep ttf
grep will filter the output and only show the lines containing "ttf", if there are no lines displayed, then there are no identical ttf files!
EDIT: You might wanna change grep ttf to grep .ttf if any of your font names contain ttf in them (e.g Nottferman, made that one up). Also it is bound to take long when doing a byte-by-byte comparison of 32k files, so just wait until it is finished.
EDIT2: Those files without an extension in the fonts directory are just files with 0 bytes of information in them, I opened up a hex editor and checked them personally. So all of them are found to be identical.