Hi Kalle,
it depends on what you call “inheritance”. I believe we’re looking at a double-class selector issue here.

That kind of selectors is generally not robust, as MSIE – for example – doesn’t evaluate them correctly either.
In MSIE, a selector like .class1.class2 {} will be evaluated as .class2{} – all elements with the class class2 will be influenced.
Likewise, in PD4ML it seems to be the first class that gets honored.

So, in my opinion, the question of your post is: does PD4ML support double-class selectors?

And a robustness hint is: try to avoid them as they’re problematic with browsers as well (at least to my experience).