Tint uses UTF8 internally. Buffers can be in a single byte encoding which maps directly to UTF16 or UTF16. Encodings which do not map directly to UTF16 are converted as a file gets read or written, for example UTF8. Currently only the basic multilingual plane is supported without any support for combining characters.
Tint Emacs only supports English. I, unfortunately, only speak English (though I have high hopes of learning another language some day), so if Tint Emacs is going to support other languages I am going to need some help. Also, there are no input methods yet.
If anyone is interested in having Tint Emacs support other languages besides English, having more complete unicode support, input methods, or other international features, please let me know. I am happy to work with you to make it happen.