Syriac diacritics

No, combining diacritics work fine. Maybe it's not actually the right character?

It is definitely the right character U+0308. I tested it to make sure, and u(0x0308) produces the same character that is in the Syriac word above.

There is probably a bug in Lua's regex implementation. I moved the combining diaeresis to the beginning of the bracket block and now it works. I tested it and it doesn't work in any other position.

Strange. Glad that you got it working anyway.