Dante, the poet, depicts the second circle of hell as more serious than the first by the difference in the atmosphere. Those in the first circle merely sighed or groaned, but in the second, they cry and moan. The lustful are forced to be thrashed about by winds, and perpetually relive their sins with no hope of redemption.
Dante, the character, is sympathetic to those guilty of the sins of the flesh. In particular, he feels a deep sadness for Paolo and Francesca, who Dante feels did not intend to sin, and should be granted leniency because it was accidental rather than purposeful. Dante , the character, is so overcome with emotion at their plight, that he faints.
The effect of this is that it separates the poet from the character. It is easy to forget they are one and the same.