Seems like <em> is styled as italic regardless of language. Different languages have different conventions for indicating emphasis. For example, <em> should not be styled as italic in Japanese because it can make the text illegible.
From what I can tell, <em> should only be styled as italic for languages using Latin alphabets, but more research is needed to figure out how <em> should be styled in different languages.
- East Asian documents traditionally use small symbols next to each glyph to emphasize a run of text.
- The preferred position of emphasis marks depends on the language. In Japanese, Korean, and Mongolian, the preferred position is over right. In Chinese, the preferred position is under right. Note: Unclear which Mongolian writing system(s) this applies to. Possibly all?
Source: CSS Text Decoration Module Level 3 - Emphasis Marks
- In Arabic, it is traditional to emphasize text by drawing a line over the letters Note: would this conflict with browser link styles?
- In Armenian the շեշտ (šešt) sign ( ՛ ) is used.
- In Ethiopic script, red is used Note: would this be accessible? would it look like a link?
Source: Wikipedia
- In Japanese, a sans-serif font, or emphasis dots (horizontal writing) and sesame (vertical writing) may be used to express emphasis.
- In the Amharic Script (Ethiopic), underlines, larger text or a different color may be used to express emphasis.
- In Tibetan, marks and colors may be used to express emphasis.
Source: Readium CSS - Internationalization – A Typography Primer - Emphasis