#dialogue characterization

We are now reading Frodo and Sam's journey in Ithilien. My partner was the one reading tonight while I dozed (and drank my herbal tea). As he voiced Faramir, he stopped and noticed that there were a few words between parentheses as part of his (direct) speech, which he didn't realize what a legitimate thing to do in classic literature. I opened my own book to see for myself, and (unless I'm mistaken), not only is this the first time it occurs in LotR (on page 673 of my edition), this happens two more times in the same conversation and once again later in the chapter (always coming from Faramir).