Björn Jadelius Wed Apr 15 08:46:19 UTC 2009:
Firstly, the manual says [1] that "markup.heading.2.html" can be used in a language grammar.
This selector is not implemented in the standard HTML bundle. To see the selectors for a given character You can press Shift-Ctrl-P.
Read chapter 13 in the manual too.
Thanks for the shortcut tip and pointers. Good to know that it is possible. If only I make a new HTML bundle or something ... ;-)