There is one passage from the chapter "Knife Grinder" that really stands out to me as an important moment in Jason's coming of age. He has just run away from the other boys, who were playing war, because he knew that if they saw him they would gang up on him. He escapes to the woods and is finally alone to reflect on himself.
Picked-on kids act invisible to reduce the chances of being noticed and picked on. Stammerers act invisible to reduce the chances of being made to say something we can't. Kids whose parents argue act invisible in case we trigger another skirmish. The Triple Invisible Boy, that's Jason Taylor. Even I don't see the real Jason Taylor much these days, 'cept when we're writing a poem, or occasionally in a mirror, or just before sleep. But he comes out in the woods. (233-234)
This is the most directly that Jason ever talks about the way he acts differently from his true stuff because of those around him. He seems to think of this as an undesirable thing, but doesn't seem about to do anything about it. However, facing the problem himself instead of just being told it is a problem by Eva van Outryve de Crommelynck. Jason certainly recognizes that he has a true self that he hides from the outside world: the Jason Taylor who writes poems and speaks in long poetic phrases. This acknowledgement of the problem is the first step towards its solution.
Also in this passage, Jason mentions that his true self comes out in the woods, and in that situation it is more than just a fleeting glimpse of the true Jason Taylor. I think this can be seen in a slight shift in the narrative voice following this passage. In some cases, his phrases even rhyme, "First every kid labels me as a tragic case, now half the teachers'll think I'm a waste of space" (235). He also gets much more philosophical, as can be seen when he encounters a bird.
A bird so near it might have perched on the curl of my ear musicked a flute in a jar. I quivered to own such an unownable thing. If I could've climbed into that moment, that jar, and never ever left, I would've done. But my squatting calves were aching, so I moved. The unownable bird took fright and vanished down its tunnel of twigs and nows. (234)
First of all, this passage starts with another lyrical, rhyming (near, ear) sentence. Then, the real Jason Taylor, alone in the woods, contemplates the fleetingness of time and wishes to preserve the purity of his moment with the bird forever. Although he is talking to the narrator, not friend or family member, I think that this shows how much more at peace the true Jason is, the Jason who doesn't have to worry about what other people think.