son commentaire = his/her comment.
ton/votre commentaire = your comment.
Asking for comments to an audience, we say: "des commentaires ?"
Anyway, "son" and "sans" are not pronounced the same. There are 4 nasal sounds in French and I suggest you get to differentiate them better by using forvo.com for example, with a sentence like: lundi matin, je prends mon temps. (note that "an" = "en" = "em")
If I propose something to an audience, "Is it easy to understand vocal inflections when learning another language via computer voice ?" Then I pick you to ask specifically, I would say, "Your comment ?" How would that be said ? If I ask you in French, would it be proper to ask you in this manner, "Son commentaire ?"
Well, Duo, and a few of the native French speakers here seem to convey the message that in France it's pretty common to ask questions using intonation alone, so I think that maybe it should work, but I'd definitely like to see what a native French would say as I'm only on day 60 of learning French.
It seems to me that "No comments" is a pretty common abbreviation for "I have no comments," such as in a response to an article, paper, or publication sent to colleagues for comments, but I may be overestimating how common it is because I use it. I used it here because "No comment" feels more idiomatic. Is this French expression used the same way "No comment" is in English?
"Cent" and "sans" do sound very close, but "cinq" sounds quite a bit different.
Try going to http://www.acapela-group.com/ Pick a French voice, put "sans commentaire; cinq commentaires" into the box, and listen. You can try more than one voice. You'll notice the vowel sound in "cinq" is quite a bit flatter; also, you can hear a teensy pause as the speakers actually make the "k" sound at the end of "cinq" before starting "commentaires".