system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] Why are Jedi that return to the light forgiven but regular criminals that repent don't have this luxury?

Seems like a double standard. See examples of Vader, Revan, Quinlan Vos.
gpt
Force users are very rare and therefore very valuable.  The movies and books tend to focus on such characters so they seem more common than they really are.  Therefore it is worth the resources to turn someone who has fallen to the dark side back to the light - to an extent.  Even among those Jedi who have fallen to the dark side the ones you have named are exceptional.  Vader is the most powerful force user there is (pre-Mustafar) and Revan is damn strong as well.  Think more of a high-level military commander or politician defecting during a war.  Killing them weakens the enemy while turning them can hurt them more AND strengthen your side.

Low level defections wouldn't be worth a mention in the grand scheme of things.  However, at least in the EU, high-level military defections are referenced.  So it isn't really just Jedi that are allowed to turn but you better have something to offer.