Why not treat initial close-as-duplicate similar to answers from a rep perspective?
50607
Reward finding duplicate questions - +10, +2, -5
116380
Should dupehammer wielders use their powers to wipe obviously incorrect close-as-duplicate votes?
15326
Duplicate explanation should encourage improvement of original
112760
Bug when marking a question as duplicate
51087
Remove votes to close question X as a duplicate of Y if question Y is closed as a duplicate of X
242
Accepting your own answer with alternative answers to be worth +2 reputation?
76517
Split reputation: one for questions and one for answers
53747
What's the appropriate reaction to an answer that doesn't attribute the source it's copied from?
78376
Flag Answer, duplicate
31654
Closing Etiquette: Why Do Some Answer *and* Close?
63097
Why should 10k rep users view self-deleted answers?
105400
What should we do about *identical* cross-site duplicates? (i.e., copy-and-paste cross-posting)
10293
How should duplicate questions be handled?
146576
Askers should be able to close their own question as a duplicate
52035
An elegant solution for "answer-stealing" edits?
89328
Is it acceptable to copy your own answer verbatim from an off-site resource?
13649
What to do with cross-site duplicates?