In the last poem of the Daodejing it is said, “Sincere words are not pretty. Pretty words are not sincere. Good people do not quarrel. Quarrelsome people are not good. The wise are not learned. The learned are not wise.” The way I would interpret the first two lines is a difference in emotion. If you are being sincere you may not particularly care about the people you are talking to’s feelings and may even appear harsh. This can especially be true with giving directions. However, if you are trying to make your words appear ‘pretty’ then you might not be entirely truthful with the point you are getting across and your demeanor; the words could lose their meaning or significance.
The third and fourth lines are more straight forward, both have to do with behavior. If you are portrayed as ‘good’ you aren’t actively seeking out an argument while if you are that does not make you a ‘good person.’ It’s okay to have differences, but you should be able to get past them in a civil manner.
The last two are a bit more difficult. When someone is called wise it usually means that they have a lot of experience in a particular aspect. Being called learned typically defines a person as having a lot of knowledge, but not necessarily experience. This knowledge could mean from school or books. If you spend too much time gaining knowledge, you’ll lack experience in everyday life. However, if you spend too much time out in the world, you will lack necessary knowledge. It’s all about finding a balance.