I used a wikitext context in my snippet thought :
$$$text/vnd.tiddlywiki
\rules except dash list
<style>..</style>
$$$
-- and : are used for css variables and for pseudo selector so it’s usefull to be able to use the rules pragma to disable the wikitext parsing in arbitrary places in a tiddler (you might want to use dash and list elsewhere in the tiddler). If you use the text/css context, the code is rendered inside a code element which disable the style inside the typed block.
It does work in a wikitext typed block, but the style tag is needed :
Unless I misunderstood your comment ?