I'm in agreement with Shog9Shog9 that this seems like a reasonable suggestion. Duplicate questions bug me... a lot, so much that during my interviews with SE it was one of the things I raised as something I'd like to see fixed or improved. I'm putting some thoughts into an answer to get some feedback and maybe flesh this idea out a bit more.
Your proposal is very close to something I have been kicking around for a little while now. The things I like about it are:
- it rewards users to find duplicates
- we can potentially still give something the user who asked the duplicate question (with the +2 accept), many times these are new users who are trying to contribute to the site and gain some rep - if they accept the other question is the solution, then I think rewarding them with something is good
- we'll have more signposts to the best question and answers
I also think there is an additional side effect that may result from this, in that, it might alleviate some of the frustration users feel when people answer duplicates. Minimizing even a little frustration is a good thing... right?
I do see a few potential problems that need to be hammered out on this.
- What happens if the question gets re-opened? Does the user who benefited from the original duping of the question lose the rep? I'd say yes to minimize gaming on something like this.
- Does the OP who asked the question also lose the rep awarded for validating the dup if it gets reopened?
- How will this work with gold-badge holders? We still want them to close obvious duplicates but there will not be a UI that is created for the OP to accept it due to the single vote. Excluding a large group of users with significant knowledge in a tag seems detrimental and might result in gold-badge holders answering questions instead of closing. Maybe, they get some reputation if the question doesn't get reopened after a certain number of days... not sure yet though.
I'm worried about potential abuse that I haven't yet thought of but I'm going to chew on this a bit more. I'd really like to see something implemented to better handle the duplicate question problem. I am going to status-review this because it's high time we do something about this.