Don’t have a running KOReader here ATM, and not the book. But shouldn’t the HTML tags correctly indicate the document language, and thus make KOReader use the correct set of typo rules?
Looks like a problem in the ebook to me, possible?
Did a quick unpack and check of one of my ebooks, where it correctly shows "de-DE":
Code:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="de-DE">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta http-equiv="Content-Style-Type" content="text/css" />
<meta name="generator" content="pandoc" />
<title>ch001.xhtml</title>
<link rel="stylesheet" type="text/css" href="../styles/stylesheet1.css" />
</head>