* in a nutshell, people ask the same conceptual question in different ways, it's good to have all those ways around to help Googlers
We've also improved finding duplicates in the close dialog since that meta post (it's a hard problem, so it's not a perfect suggesting system), so it's hardly like we've done nothing.
Also, as written that feature request is unworkable. Incentivize closing over asking, madness. Even incentivizing over editing (+2 up to 1k rep) is harmful IMO. I suppose we could just decline that post, but what'll probably happen is it'll be status-completed when we've come up with a better solution (which will be documented in an answer).
^ Based on the most recent data dump, somewhere around a 15 - 20% of closed questions (which are about 3-4% of all new questions). That sounds about right, honestly. I'm sure some stuff is slipping through, and we could make it easier to maintain these rates; but it doesn't seem like a pandemic of duplicates.
Oops, forgot the disclaimer: Stack Exchange Inc. employee, etc. etc.
The duplicates issue is something a little more complicated than just having a canonical answer for everything and it comes down to the naming problem. People understand things in different ways, so having multiple ways of asking the same question, and different explanations of the answers can be very beneficial.
Before looking for duplicate questions, it should be easy to reduce them by improving the Search.
I believe it is very hard in SO to find if a question: adding words in may request should reduce the number of results instead of increase it. I mean "C# Dictionary performance" should be same than "+C# +Dictionary +performance".