How does Dante utilize the depiction of characters in The Inferno to express social satire and satirical commentary?
It's awesome that you're reading Dante's Inferno—it's a great and super important work!
Satire is the use of irony, humor, and exaggeration to expose hypocrisy, stupidity, or evils. Social satire is when you do this in the context of your own society.
If you are familiar with the Daily Show and the Colbert Report, this is a great way to think about satire. In the Daily Show, Jon Stewart directly makes fun of issues in our society. But in the Colbert Report (so sad it was cancelled!), Stephen Colbert would pretend to believe in the issues he was intending to mock, and would exaggerate them in a funny way to make his point.
Dante does the same thing in the Inferno. He exposes the hypocrisy and malice in Florentine society by showing how the people atone for their sins in hell—it's pretty extreme. He does this for groups in general, like in the third circle where the gluttons are punished. He also does it to specific people, like Filippo Argenti, in the fifth circle, where anger is punished.
Argenti was someone who had wronged Dante, and rather than just talk about that directly, Dante goes to an extreme and shows Argenti paying for that sin in hell.
Look for more examples like this—there are a lot of them!
Dante had reasons to use social commentary--he was exiled from Florence for picking the wrong side in the Guelph-Ghibelline conflict and for this was threatened with death if he came back to Florence. In The Inferno, Dante sends the people who committed various sins into their own circle of Hell. Each circle fits the crime. Gluttons are left to wallow about in waste. Lustful people are blown about by the winds, as they cannot stay attached. Murderers and suicides get their own grisly punishment. Dante sends many people who have wronged him into Hell. There are even popes in Hell. Even in the lowest circle, the most treacherous people in his view of history, Brutus, Cassius, and Judas Iscariot are being chewed by a three headed Satan-like beast encased in ice, which is supposed to be the exact opposite of the Trinity used in Christianity. Dante wanted to write an epic for Florence that would be the equal of the ancient Greek and Roman epics. He also wanted to state to his enemies that their eternal punishments would fit the crimes.