adjectives - "I feel bad for you" versus "I feel badly for you"

I have a sense that "I feel badly" is acceptable. Native English speakers use this, who are not of low intelligence or poorly educated.

It's clear that either way, the semantic idea is that the speaker is experiencing an uncomfortable feeling.

A feeling is abstract: it can be regarded as a state or something that is happening. We don't really know what it is other than through subjective experience.

The linguistic tools for expressing it briefly (not using circuitous language like "I am experiencing an uncomfortable feeling") boil down to using an adjective or adverb: bad or badly.

Neither of these choices is a perfect fit.

"I feel bad" maps the "bad" adjective onto the speaker. So if "I feel stupid" means "I feel that I am stupid" then "I feel bad" should mean "I think that I am bad". But it doesn't.

"I feel badly" maps the "bad" onto the feeling regarded as an action that is going on. This is imperfect also. ("I feel badly" versus "I drive badly".) But there are also: "Think badly of someone" or "Speak badly of someone". The arguments against "feel badly" must take into account such examples also.

Neither choice precisely pins the badness onto the involutarily experienced emotional situation.

But between these two choices, representing the badness as an attribute of the feeling-action (necessarily an adverb) seems semantically cleaner than as an attribute of the noun (adjective) denoting the subject who is experiencing the feeling (involuntarily, at that). The feeling-action is closer to the meaning.

This is probably why some people use the "feel badly" construction; it seems to them that "I feel bad" is like "I feel that I am bad", but "feel badly" is like "think badly": having a negative feeling analogus to having a negative thought.