In case the authors are here, the first sentence contains the bytes e2 80 94 which would be UTF-8 for an em dash, but it has been reinterpreted as 3 bytes using https://en.wikipedia.org/wiki/Windows-1252#Code_page_layout and shown on the page as —. Further down, there's a lot of similar errors such as a single right quote (U+2019) in K'nex. Firefox seems to have first removed their encoding configuration menu in version 89, then introduced a new button in version 91, and that one is disabled now as well so there's no fixing this user-side it seems :/

Edit: ah the page is from 2012-03-19, from the <meta property="article:published_time"> tag