[famfam]

Originally Posted by Doitsu

...Try converting your test case epub to a kepub book with Calibre.
... your stylesheet might contain errors and/or another selector overrides the pseudo selectors.
Did you use the Validate with W3C Sigil option to check your stylesheets?

kepub-converting hat no effect on it.
Here the check of stylesheet results and the errors:

Spoiler:

W3C CSS Validator results for TextArea (CSS level 3)
Sorry! We found the following errors (7)
URI : TextArea
6 body Value Error : orphans 0 is not valid, only values greater than 0 allowed. : 0
6 body Value Error : widows 0 is not valid, only values greater than 0 allowed. : 0
11 Parse Error } { line-height: 10.0pt; }
13 .BalloonText Value Error : orphans 0 is not valid, only values greater than 0 allowed. : 0
13 .BalloonText Value Error : widows 0 is not valid, only values greater than 0 allowed. : 0
14 .ListParagraph Value Error : orphans 0 is not valid, only values greater than 0 allowed. : 0
14 .ListParagraph Value Error : widows 0 is not valid, only values greater than 0 allowed. : 0

Valid CSS information
* {
padding : 0;
margin : 0;
}
body {
font-family : 'Arial Unicode MS', sans-serif;
font-size : 12pt;
}
p {
margin : 0;
}
li {
margin-bottom : 0;
margin-top : 0;
}
h1, h2, h3, h4, h5, h6 {
font-size : 1em;
line-height : 13.0pt;
}
.BalloonText {
color : #000000;
font-family : Tahoma, sans-serif;
font-size : 10pt;
}
.ListParagraph {
color : #000000;
font-size : 10pt;
margin-left : 36pt;
}
span.Hyperlink {
color : #0066cc;
text-decoration : underline;
}
span.SprechblasentextZchn {
color : #000000;
font-family : Tahoma, sans-serif;
font-size : 8pt;
}
img {
max-width : 100%;
}
p::first-letter {
font-weight : bold;
}
Congratulations! No Error Found.
This document validates as CSS level 3 !
To show your readers that you've taken the care to create an interoperable Web page, you may display this icon on any page that validates. Here is the XHTML you could use to add this icon to your Web page:

<p>
<a href="http://jigsaw.w3.org/css-validator/check/referer">
<img style="border:0;width:88px;height:31px"
src="http://jigsaw.w3.org/css-validator/images/vcss"
alt="Valid CSS!" />
</a>
</p>


<p>
<a href="http://jigsaw.w3.org/css-validator/check/referer">
<img style="border:0;width:88px;height:31px"
src="http://jigsaw.w3.org/css-validator/images/vcss-blue"
alt="Valid CSS!" />
</a>
</p>

(close the img tag with > instead of /> if using HTML <= 4.01)