"I could concentrate more on the unspoken intricacies between the two protagonists."

Thats in fact part of the problem I had with the film: I just didnt think that there were enough moments where Ozon allowed us to contemplate their interactions. His characters seemed rigid, boxed-in, like they werent allowed to grow on their own; instead they were dependent on the films backward chronological structure.

"At one point we see Marion (the female lead, played by Valeria Bruni Tedeschi) having a sexual encounter with a stranger in her wedding night. We see how she wonders, if she really loves her husband, if she can do without touching another man again, and probing these questions through this opportunity."

Thats true, but I think this scenario truly depends on whether one finds her actions plausible. Perhaps Ozon couldve chosen another set-up in order to elicit her emotions... I'm not sure. On the other hand, this film is about challenging, and even attacking, the notion of fidelity.

"Here he displays more his humanist side, making us understand and "forgive" both parts more or less equally."

Interesting. But one could also make a case that Ozons characters are actually quite hollow, both morally and emotionally. And he perhaps doesnt do enough to justify their behavioral patterns.

I will say that I remember 5 x 2 better than some of the other films I've watched (and liked) since then. Maybe it's a sign.