This question made note that David acts in a deceitful manner towards the priest when he goes to ask for help as he flees from Saul. This isn't the only time, however, that deceit is a feature in David's ascension to the throne. In 1 Samuel 19, Michal helps David escape from Saul's men by dressing up an idol in his bed and letting him escape through the window. In chapter 20, Jonathan and David create a ruse wherein Saul is told that David has gone home to sacrifice with his family. In chapter 21 we have the already mentioned story with Ahimelech and then another where David pretends to be a madman so that Achish king of Gath does not kill him. Even the very beginning of David's story starts in this manner, oddly with God telling Samuel to tell Saul that Samuel is simply going to Bethlehem to make a sacrifice.
Since this is clearly a recurring theme, what is the author trying to communicate through it?