I've borne witness to three of these controversial moments. I've heard Jack utter 'Fuck me' in the first tent scene (he actually says it twice), I've seen Jack clasp Ennis's hand in the first tent scene, and I'm almost positive Jack says 'I'm sorry' in the second tent scene (some people swear that 'I'm sorry' isn't there, but I heard it on my first viewing, and in every subsequent one).
I didn't catch the handholding until I purchased my DVD copy, and had to watch the scene twice before I caught it--in the cinema, the scene was too dark to make this detail out, and even in the digitally lightened transfer, the gesture occurs so quickly it could easily be missed. It adds a whole new dimension to the emotional tenor of the boys' relationship at this early juncture, mitigating the animal lust of the moment with tenderness and affectionate yearning.
I didn't hear Jack's effin' plea until a friend of mine clued me in, and I had to watch the scene on DVD a couple of times before catching it. It's so subtle as to be barely noticeable, but again adds to our understanding of Jack's character, further suggesting his worldliness and experience relative to Ennis's.
Amazing that over half a year later, we're still discovering nuances to this film. How many more may there be, one wonders?