An interesting question was asked over on FB this mornng. I am stealing a bit from Jim Barker's forum.
..."Are you dating someone?" asked Scott casually.
..."Ashley was absolutely not involved," stated Rene firmly.
..."I don't see what you are referring to," said Scott, puzzled.
Note that "casually" and "firmly" do not need a comma whereas "puzzled" does.
One of the questions was whether the "-ly" creates the need for a comma.
The commas are not about the "-ly," per se, but about the fact that these words are adverbs. They modify the verb "asked" and "stated." The difference between those and the word "puzzled" is that "puzzled" is an adjective, a participle. The participle takes a comma because it is a nonessential element that tells you about the subject, Scott, which is a noun.
Happy punctuating!
Margie