Ok, so a good way to do constructive feedback is to point out something you like, something they could improve on, and your overall impressions. So from your original post I would have said this about our game.
"I though the visuals worked well in your game, I had a hard time figuring out how the stealth worked, it would have been nice to have made that more clear. I also could not figure out how to leave once the springs were collected. Good start to a game, I hope you learned some things and I can't wait to see your next game jam game."
It keeps the tone positive, it leaves out the comment about other comments which did nothing productive. And when a game points out something they messed up that means they are aware of it so there is not really a need to point it out, so pointing out you had to give us a bad audio score added nothing to the posting. You don't have to lie or sugar coat, but keeping it positive does wonders to not hurt motivation when giving feedback.
I hope that helps :)