Cantos 31-33

Canto 33 line 85
Their youthful ages made them innocent!

This line made me think about where the children go when they die young. Obviously they aren't completely spared from punishments or from Hell, as mentioned in Canto 4. Limbo contained children who were not baptized. However, Dante encounters mostly adult souls, people who either knew or were supposed to know of their sins. So, are children always held accountable for their sins even if they were not aware that they were committing them? Is a child's ignorance to the "rules" an excuse for sinful behavior? I wonder if it was purposeful of Dante not to include many descriptions of such punishments of children. Perhaps this would have been too much, and perhaps he would have lost some merit or some readers. Including descriptions of suffering children would certainly bother readers more emotionally than any other passage. It would also show better than any other passage the unfairness of Hell.
Perhaps all children truly are innocent, and perhaps they're the ones who go to heaven.

Canto 33 124-130
Know that as soon as a soul commits betrayal
The way I did, a devil displaces it
And governs inside the body until its toll
Of years elapses. Meanwhile, down to this vat
The soul falls headlong-so it could be true
That this shade, wintering here behind me, yet
Appears above on earth too

I found this passage interesting because in this instance the soul who is being punished has not even died yet (or his body hasn't at least). The idea that you can start your eternal punishment before even completely leaving the earth is interesting. It brings the idea that one can be punished at any time, and death is not necessary to begin this punishment. This passage is also very sad because of the feeling of loss the person has towards what was taken from him, the remainder of his life. It's interesting how a devil replaces the soul inside the body. Why isn't the body just killed? Is this in itself another form of punishment (knowing your body is living on without you)?
I especially would like to know how this devil behaves in someone else's body. Would he personally try to create conflict in the sinner's life? Or does he simply take advantage of living life in human form (something he can no longer experience)?
Do the person's friends/family ever notice the change?