In the first reading vv.16-18 understandably give interpreters fits. (The Lectionary ends the reading at v.14, one way of dealing with the problem!) We might wonder about these verses in the context of other nearby verses:
“Surely oppression makes the wise foolish,
and a bribe corrupts the heart.” (7:7)
“Do not be too righteous, and do not act too wise; why should you destroy yourself? Do not be too wicked, and do not be a fool; why should you die before your time? It is good that you should take hold of the one, without letting go of the other; for the one who fears God shall succeed with both.” (7:16-18)
“Surely there is no one on earth so righteous as to do good without ever sinning. Do not give heed to everything that people say, or you may hear your servant cursing you; your heart knows that many times you have yourself cursed others.” (7:20-22)
In light of vv. 7, 20-22, I think William Brown’s on the right track re vv.16-18: “Qoheleth exposes all efforts to fulfill the absolute ideals of righteousness as self-serving attempts to reap glory. A life obsessed with righteousness, in fact, blinds a person from his or her own sinfulness.” So Thomas Keating, author of numerous books on centering prayer, tells of the young man who proudly drank everyone else under the table, and, on becoming a monk, when Lent came around, equally proudly fasted everyone else under the table. (The next year his abbot prescribed a penance of a full glass of whole milk and a large Hershey’s bar daily!)
So I might wonder: in what spheres or regarding what issues am I tempted to present myself as better/more woke/[insert preferred adjective here] than I in fact am?
In passing, v.7 may be important for our reading of the book as a whole. The teacher is immersed in an oppressive context; readers may properly wonder what effects this is having on his wisdom.