What does this reveal about Jesus?
He not only drives out demons, but heals the effect they've had.
Notes & Applications:
As I noted in the previous miracle, there were those who reckoned Jesus to be in league with the devil. This was a dangerous proposition as blasphemy against the Holy Spirit was unforgiveable. But it's clear that they were not making an objective evaluation but simply were desparately trying to discredit Jesus.
The effects of demon-possession took various forms. In this case it made this man mute. Today the secular psychologists and such people (whom I would like to refer to as "psycho-Babylonians") would propose the origins of all such handicaps to be psychological or physicological, but there is also a spiritual aspect to consider that the materialists overlook. Their analysis may end up confusing root causes with symptoms.
There is also an allegorical application to this, as with all the miracles. In this case I would say that some are afflicted with the inability to express themselves. I personally have experienced deliverance in this area to a degree, as in my youth I had been regarded as inept in communication skills whereas now I find they'er a bit more enhanced.