The Green Knight comes to Arthur’s court, he claims, because he’s heard of the reputation for bravery of its men, the Knights of the Round Table. He uses the threat of damage to this reputation to force the court to join in his beheading game. Similarly, Lady Bertilak convinces Gawain to kiss her by touting his reputation for courtesy, yet takes the tactic one step further by implying that Gawain is not Gawain if he refuses. This strategy relies upon a definition of identity as composed of your reputation - of what "everyone says" about you. Yet this definition of identity can be dangerous, since it gives other people a great deal of power over who you are. This precarious situation is demonstrated by Gawain’s attempt to avoid Lady Bertilak’s seduction without appearing discourteous. On the other hand, the narrative strategy of Sir Gawain and the Green Knight relies upon collective opinion to back up its claims. For example, comments about Arthur’s nobility or Gawain’s virtue are backed up by "what everyone says."
The narrator of Sir Gawain and the Green Knight uses reputation as a tool to make his assertions seem authoritative.
Sir Gawain uses humility as a means of countering an identity constituted by his reputation.