Clint Barton fully possessed in The Avengers or not?
That question in the ask of course is always an uncertainty, and that’s why I wrote in the posting leading to this question, it’s canon “for me”.
I consider deleted scenes canon as long as the material in it does not contradict the movie (ie with a scene worded completely differently or a scene not fitting in the movie timeline).
If a deleted scene fits in the movie, I consider it for myself cut out of “too little time” reasons and consider it therefore canon.
I admit, I don’t really watch bonus material except for deleted scenes, it doesn’t really interest me. So I can’t say how Marvel feels about its cut scenes.
In the case at hand, Fury’s conversation with the council had a few lines more in the additional scenes that don’t alter the conversation itself. So I think, for myself, they got cut to straighten the scene, make it shorter, not because they wanted it to look like Clint was completely possessed the whole time.
Not only for this scene, I definitely do think, Clint was not fully possessed. He not only did not shoot Fury and Maria (though Maria dodges off quite well).
He also did shoot the building guards in Stuttgart only in the shoulder. That one guy probably wasn’t dead and the second one only because he fell off the roof. That’s for me pretty much a sign, Clint fought Loki off as best as he could.
And all this doesn’t even consider his deleted scene with Loki where it’s simply pretty obvious, he’s lying when he says, he missed the kill shot. Clint doesn’t miss.
I’ve uploaded the full deleted scenes and the gag reel from the first blu ray version a few months ago. Unfortunately I don’t have the rest. You don’t get the latest blu ray box in European coding, and I refuse to buy all of them new for a few minutes of material. But I have the old ones on my account months at least. You can find the scene in question (it’s a masterpost, all the other deleted scenes and the gag reel are linked) here.
I hope this helps.