Quick answer
The chapter ends on a joke with a serious edge. Silence will make a fool look wise, which says something about both silence and talking.
Read both lines
The humor is real and the observation underneath it is not: nothing exposes a person faster than speech, so withholding it conceals more than any other strategy available. Both lines carefully say counted and considered, so the verse is describing a reputation rather than a transformation. He is not wise; he is thought to be. And the practical point lands on the reader rather than the fool, since a book that has spent chapters on the damage a mouth does closes this one by noting that the simplest remedy is available to absolutely everyone.
Related: Proverbs 17:27 · Proverbs 10:19 · Proverbs 11:12 · James 1:19
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.