(Proverbs 15:4 KJV) A wholesome tongue is a tree of life: but perverseness therein is a breach in the spirit.
I think this is another approach to the thought of verse 2. A “wholesome" (soothing NASB) (4832) “tongue” (3956) can be a good thing. Notice I did not say “is” a good thing. More on that in a moment. Proverbs is full of reminders that it is better to be a peacemaker than an agitator. Jesus said, “Blessed are the peacemakers.” This has the idea of healing. Think of the first aid cream in your cabinet. Think of petroleum jelly and all the soothing it does. Our mouths can be that way. We can calm angry people. We can avoid stirring things up. This is supposed to be a good thing.
But.... And it is a big “but.” A soothing tongue can also be a “perversion” (5558). Based on other passages in Proverbs, this is a deliberate goal for some people. Perversion seems to have a consistent meaning. It is a twisting. Remember that much sin is a warping of a normal, God-blessed, activity. Yes, we are to sooth and heal, but what about the times when the need is for reproof and rebuke. What do you do when a brother in Christ needs correction and you are the person that God has directed to speak. Part of love is doing what is right for the other person, not what is easiest. What if Jesus had always followed the soothing route? The rich young ruler would have never known the truth. Peter would have not been corrected. The Pharisees would have continued being smug and deceived. Pilate would have been untroubled. The list could go on.
So? It is best to be a healing influence, except when surgery is needed. In medicine the least invasive technique is best. The same is true in our spiritual lives. But remember that when the Holy Spirit demands more than a band-aid then a band-aid becomes perversion.