QWebView font rendering bug on fh-worms.de (letter spacing)

When showing https://campus.fh-worms.de/~progbau/Routing/05/index.html with QWebView (e.g. with the browser example) on Archlinux, there are weird spaces between the letters (see attached screenshot).

Once it also happened that there were spaces between words, and text jumped while marking it, but I can't reproduce that.

The page looks fine in a WebKitGTK+ based browser (dwb). It also looks fine with Qt under Windows, and unter Arch when ttf-ms-fonts isn't installed (but then I get a completely different serif font).