Pain is a textbook example of a quale, and "pain" describes an effect, a reaction, not a cause, which would be something like "sharp" or "hot". Likewise, words for tastes barely map onto anything object[ive]. "Sweet" kind of means "high in calories", but kind of doens't, since saccharine is thousands of times sweeter than sugar, but not thousands of times more calorific. And so on.

And as I pointed out in the other thread, our experiences change in response to the relationship between viewer and object even as the object neither changes nor seems to change. We have the ability to be aware of internal states which are intimately involved in, but not informationally exhausted by, cognition of the external world. From a point of view valuing only knowledge of the external world as such, qualia are pure "noise".

But of course, it makes good evolutionary sense for us to be aware of some internal states. (And even if it didn't, evolution was never the perfect designer (witness flea wings and human appendix).) A cognitive system with a penchant for learning might easily take notice of its own internal workings during acts of perception. Such self-awareness might be extremely useful for a social animal. So you are quite wrong to assert, elsewhere in the thread, that subjective qualities would not be expected on the hypothesis of physicalism.