Steps to reproduce: enter `–` in the wikitext of the page
Expected result: an en dash (`–`) is displayed.
Actual result: `–` is displayed (on the HTML level, `&` gets encoded into `&`.
The relevant spec is [[ http://www.w3.org/html/wg/drafts/html/master/syntax.html#consume-a-character-reference | consume a character reference ]] in HTML5, which has a compatibility table for frequently used character codes which are not Unicode code points. (En dash is U+2013 so the straightforward representation is `–` but the HTML5 standard also acknowledges Windows-1250 codes for a number of characters which when interpreted as Unicode would result in unprintable characters - U-0096 is "start of guarded area".) MediaWiki should respect that compatibility table when encoding references.