An honest answer is like a kiss on the lips (v26).
In this context, a kiss on the lips was reserved for those known well and loved deeply. The proverb is saying that an honest answer is to be regarded as a precious expression of love.
We Brits don't do honesty - saying what we really think is considered impolite. So an 'honest answer' needs something of a renaissance.
We should love people enough to give them an honest answer. If they look ridiculous in an outfit, and they ask, we should tell them. More importantly, if they gossiping, envious, prideful or just being plain stupid, and they ask our opinion ... you must 'kiss them with confidence'!
The key to all this is to wait until you're asked. Remember that giving your answer before being asked can feel like a body-slam rather than a cheeky peck on the lips!