The kf8 format indeed accepts small-caps. Of course, the text to be in small-caps must be "correctly written". If the original text is all in capital letters, then you won't see small-caps. The text must be written with the first letter as capital and the others as lowercase letters. So:
<span class="sc">TEST</span> -------------> INCORRECT: won't show as small-caps
<span class="sc">Test</span> -------------> CORRECT: will show as small-caps
The question is: how did you build the .mobi file? With Calibre? If so, that can be the source of your issue. Try building the .mobi file with kindlegen (or kindle previewer).
(I suppose you are using a kindle device that supports the kf8 format)
|