2016-12-08: this section is preliminary.
HTML output works well if your source includes Unicode characters. Hyphenation is a non-issue, since text reflows and there is no flush-right support.
It is a different story for LaTeX, PDF, and print. So that is the focus in this sample document. You may not recognize the next subsection, but an explanation follows.
ὁ δὴ ἤτοι πρῶτός ἐστιν ἢ οὔ.
The previous subsection has an xml:lang attribute on the subsection element, whose value is el indicating the Modern Greek language. So the entire subsection is being treated as characters from that language. There is a title, but it is not being affected now, and so is empty.
The behavior should be entirely similar for part, chapter, section, and subsubsection.
Other elements have language support. We are starting with foreign, which also italicizes the content.