Just because I can, and to deepen the pain, I'm trying to rearrange the takes that make more sense in the progression of Dean's eye wetness, dialog and lighting.
The way Cas is talking about "the thing" that he wants while looking at Dean. Is my current bittersweet torture. His eyes sparkling like he is watching the most beautiful star. The brief smile because he has "it" in front of him, the most wonderful creation he ever saw in his time on earth. The half sight because he is more convinced now that Dean is "the thing" that he wants. Dean is his happiness and he is starting to feel it.
I mean look at him....
Makes me want to scream into the void. Of course it's a love beyond measure in space and time. It's the absolute realization of him being nothing and Dean being everything for him. It's Castiel angel of the Lord ™ acknowledging his vast and everlasting existence, beeing invaded by this miniscule human who is everywhere inside him.
The best response, is Dean's confused face when he hears the last phrase: "Something I know I can't have"
I think this is the "homofobic" or "disgusting" face some "critics" or "meta writers" or "desperate Wincesters" that were melting and chocking in their own foam when they were watching this poorly lighted scene. Who made memes from it the very night or next day the episode aired.
Watching this with a better lightning and tracking the consistency of Dean's progression of tears. And with my certified authority as an old Clown in this rodeo. I conclude that we have two possibilities:
Dean expression is because an obvious confusion about everything he is absorbing from every word Cas is saying. Remember, my first theory is that he was the one about yo spill the beans and say HIS FEELINGS for Cas first, because he was convinced at that moment they both were going to die. Till then he wasn't aware of Cas feelings as explained by the Jackles this past weekend. Therefore, confusion and incredulity were and obvious progression of his reaction while Cas was laying his feelings for Dean. A sense of incredulity for this affection, this love he can read in Cas's eyes that clearly isn't just a Bro-love. Because even him, Dean I'm not whorty of love Winchester, can interpret this words as he listened from Cas lips and read from Cas's eyes.
He already catch Castiel's point and understood the meaning and direction of every word he was saying. He knew Cas was winning him on the "last day on earth" love confession. Therefore, acknowledging the feelings being exposed word by word by Cas in front of him. Hearing Cas saying: "He can't have the thing he wants". CASTIEL CAN'T HAVE DEAN. Evoked this gesture of confusion from Dean. To explain, I propose the following Dean's inner dialog:
"Why do you think you can't have me?"
Or
"What makes you think you did not have me since long ago"
Now you know why I have to share the pain, and then retrieve to my personal pit of despair. To keep editing the shit out of this, while eating glass that may be more confortable than thinking about all the What if-s or Maybe-s that could happen that night, or really happened but were intentionally hidden in the editing and poorly lighten scenes.