That's such a wonderful scene -- whoever is first showing the affection, there's definitely chemistry there. (There was a moment from that scene in the trailer, and I think it was used to hint at the developing relationship as much as the clips from the first tent scene or the reunion.) I haven't caught the gentleness from Ennis's hands, but there are all sorts of other indications of affection before that moment. That's right after Ennis orders the soup he doesn't like because Jack is sick of beans, and (as goadra/Barbara mentioned), it's right after Jack looks worried when Ennis isn't in camp.
I don't think Ennis knows or understands what he's feeling at that moment, but I think he's already fallen in love. (Jack, I think, knows he's attracted to Ennis... but I don't think Jack knows just how hard he's going to fall for this guy.)
(Pierre, have I said hi? I'm glad you're starting new threads with your observations... it's a breath of fresh air. So welcome!)