I think that "I feel badly that he is sick" is correct because the word badly modifies the verb FEEL: How I feel. Someone suggested that "I feel bad that he is sick" is correct because the word BAD goes back on ME--not on my feeling. Can someone explain which is correct and why?
Please refer to this post on ELU
In general, the verb "to feel" will take an adjective when describing the actual feeling (what you feel), and an adverb if modifying the ability to or process of feeling.
I feel bad about the results of the election.
I feel strongly about the results of the election.
For this reason, you will rarely see "feel" followed by "badly" because of the confusion over what exactly you are trying to say. Instead of saying "I feel badly" (to indicate loss of feeling), we would say something like:
I have trouble feeling ...
I lack feeling (in my ...)
I'm unable to feel ...
In the same way we would usually say "I feel good", and not "I feel well".
Of course there are many who will argue that this is improper English and insist on using the adverb (I feel poorly, I feel well, etc.) to describe their current physical condition. I can't say this is wrong, but, at least these days, it is not typical
[Edit] In the novel I'm currently reading, one of the British characters says, "I'm sorry you feel badly about ..." So perhaps you can use "bad" if you want to sound more American, and "badly" if you want to sound more British? We can ask an Australian as a tie-breaker.
sense verbe, feel strongly have a definite or strong opinion about sthg To describe the quality somethin
I feel badly that he's sick.
I feel bad that he's sick.
Both the sentences are correct grammatically, but the use of the adjective bad in front of the sense verb "feel" is more common and idiomatic.
(strangely enough, according to The Free Dictionary, badly is also an adjective. I feel badly for his loss).