I hardly know how to describe this. Consider the following reduced case:

<html xml:lang="en" lang="en">
<head>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
    <title>Kipper's Game</title>
   <style type="text/css">
@font-face {
    font-family: "Fairfield LT Std"; 
    src: url('fonts/FairfieldLTStd-Light.otf');
}

h1 {
  font-family: 'Fairfield LT Std';
  font-variant: small-caps;
  text-transform: lowercase;
  word-spacing: 0pt;
  }
  
   </style>              
</head>

<body>
<h1>BARBARA EHRENREICH</h1>
<h1>BARBAR EHRENREICH</h1>
<h1>BARBA EHRENREICH</h1>
<h1>BARB EHRENREICH</h1>
<h1>BAR EHRENREICH</h1>
<h1>BA EHRENREICH</h1>
<h1>B EHRENREICH</h1>
<h1>EHRENREICH</h1>
<h1>barbarar</h1>
<h1>barbara</h1>
</body>
</html>

In the first, third, and fifth lines, a strange character (looking like a box with an X) is inserted between the words. In the last case, it's inserted after the word. If you remove the letter-spacing of zero, the weird character appears in a different place on those same lines.

The character, as best as I can tell, is U+DBC0 followed by U+DC00.

PDF rendering attached. You can ask me for the font if you don't have it

So, so weird...

This does seem specific to the combination of font, text-transform, and font-variant. But so very strange that it depends on literal content!

1. weird.pdf‎ 32.4 kB

That is weird, would you be able to email me the font in question? Perhaps there is something funny going on with the small-caps substitution.

There is more weirdness. All characters are displayed twice and the preview app on the Mac doesn't show the X-like character.

1. weird.png‎ 19.9 kB

The characters getting displayed twice is presumably unnecessary fake bold, which can be fixed by specifying font-weight: normal for the h1 elements or using the latest build of Prince and specifying font-weight: bold for the @font-face rule or just disabling fake bold with --no-artificial-fonts.

The X character only seems to show up in Acrobat, no other PDF viewer shows it.

We have a fix for this issue in the latest build! Thanks for letting us know about it, definitely a fun one to track down.