I suppose both the narrator of this piece and Jacob could be said to have a beast element to them, both perhaps have less than satisfactory relations with their fathers, both, in a way, engage in some self-blame, and both, in some way, could be said to be in a bricked-in place at the conclusion of their respective pieces.
But. I nonetheless see the pieces extremely differently, and I never once thought of Thorn Forest until you mentioned it.
I see Jacob as a dog who's been beaten too many times. Jacob might have nipped, angry ears, but he seems on the defensive to me. To the extent he's angry, it's at those who mistreat him -- and even so, he cowers and suffers in atonement because at some level he sees the abuse as his due. Whereas this narrator is furious at the idiocy of those around him. (Note that it is not the cruel and inhumane he rails against -- it is the dull and dissolute.) He is not cowering. He is in no way atoning. Whatever he might think he deserves (he does, after all, see himself as a "lesser human being"), it is not the company of the vapid wastrels with whom he finds himself afflicted.
Jacob doesn't want to smash anything -- he just wants to be left alone. Even when attacked by the preacher, he does not fight back. This narrator doesn't smash anything, nor (if I'm right) will he -- but the impulse is there. And though he sees himself as a "lesser human being" because of his less than kindly response to dullness and dissoluteness, I don't think he sees himself as deserving punishment (as Jacob seems to do). He is not sorry.
This narrator would see Anna absolutely as she is. Actually, he might possibly find her kind of hot in her own way. (Indeed, I'm sure she is hot in her own way.) But he wouldn't see an angel, as Jacob does. He would not idealize her. He'd see her just as she is, and would take her, if he took her at all, on those terms.
Jacob put himself in a bricked-in cell out of a spirit of atonement, love, and self-sacrifice. This narrator is deliberately barricading himself off in a defensive fortress (not a prison) to get away from the shallow prattling mob.
This narrator doesn't, to me, have the sweet, tragic qualities Jacob has. But he sees things, including himself, with an intelligence and pitiless clarity that Jacob doesn't (unless Jacob gains some insight while in prison, which I think is quite possible, and is likely why he leaves Anna's letters unopened).
Jacob, I want to rescue. This narrator, I want to be at the same cocktail party so we can exchange barbed remarks in a corner. I wonder if he's single.
Sorry, William. This would be at least the second time I've gone off on a tangent claiming insight into one of your poems. I am a presumptuous trollop. Chastise me as I deserve.