Oscar:

I don't really see where we disagree, except that I judge Tarnation on aesthetic grounds and find it shapeless and in bad taste, and you don't usually do that. My point was not to condemn the film but only to describe it. I noted that it is going to be an influence and will stand as the first of its kind. On the other hand when you talk about this kind of film, the therapist is always there. .
A 20-years-in-the-making autobiography in the form of an underground film, one that has absorbed a variety of influences from what was once called the "avant garde". Techniques that have infiltrated pop culture mostly via music videos. It's a video diary from someone who found an outlet of expression at an early age within the fringes of the art world. Mr. Caouette has chosen to present the material in raw form, with only intertitles to provide a bit of structure and chronology.
Of course. I could nit-pick too--about what "twenty years in the making autobiography in the form of an underground film" means, for example. My impression is that he put it together recently. If you mean he was living his life, that's not making an autobiography, it's just living. Either he had a lot of material, in which case it's not in "raw form," but rather highly edited, or he had very little material, in which case he was not doing anything very elaborate in the way of filmmaking up to this, about his own life, so he was not working on a "twenty years in the making autobiography". But the rest of what you say is true.
Processing and interpretation of the material is almost completely the viewer's job
It always is. The question I was asking was whether the filmmaker has done his job leading up to the viewing.
First, the film can be viewed as a son's attempt to depict his relationship to a mother who was in one or more ways, absent.
That hardly needs pointing out. As I said, this is "his film’s obsession, his great subject."
…you see how it can be argued that Tarnation has a sort of "happy ending"? Taking into account what Mr. Caouette endured, I found it remarkable that he seems quite capable of developing supportive, long-term relationships, that his interactions with family members are free of recrimination and blame.
Certainly, and I noted that too--I suspect that his picture of his life is rather one-sided, that he has strengths to have the good relationships which don't fit into his focus and so we get only glimpses of them. He focuses on his life as dysfunction, which is hardly unjustified by the evidence he supplies, but this is not in any sense a complete picture of the man's life or one with any perspective. Whether his attitude to his grandfather is as neutral as you say, we shall never know.

Perspective is what Nathaniel Kahn provides, when he goes in search of his father. But he had an advantage as well as a disadvantage. He had the great disadvantage of being largely ignored by his father. But he had the advantage of distance that this provided, and the result of that distance and all the time taken to cross it is a film that provides us with understanding and love, as well as admiration for a great artist who was an imperfect man. I find that much more interesting. But it was not my purpose to condemn Jonathan Caouette for not being Nathaniel Kahn. I only mention My Architect as an example of a young man's autobiographical film that has infinitely more depth and provides an infinitely richer experience to the viewer.
I understand how one would experience frustration at so much left unsaid, at leaving the theatre with too many questions.
I don't believe I said that at all. I was not talking about my emotional experience except to note that certain moments were particularly unpleasant to watch. I had no questions. The film provoked not curiosity but repugnance. I was simply glad that it was over. I would not want to watch it again. My aim was to note its importance, to critique it aesthetically, and to point to something better that we can watch. But I am not claiming Tarnation is without interest. It represents a phenomenon. In its way it's original. It was worth writing about or I wouldn't have bothered.