My guess would be the wiki software is doing the translation automatically.
A lot of Web CMS systems and front-end systems will automatically use typographers' quotes, en and em dashes, and so on. I think even the newest version of TinyMCE, an open source text editor used by lots of software, does that. Many major sites like Quora automatically do dash, quote, and ellipsis conversion.
If you have contributors using all sorts of other languages, that's proof you don't need to worry about dashes and ellipses. Regular ASCII includes only English characters without accents. If they're worried about en and em dashes, they should also be worried about accents, and any non-English symbol or alphabet is right out.
