I'd like to talk a bit of the history of the forum.
Before 4.0 the concept discussions were structured in a quite different way.
There was only one discussion thread for each faction and most important of all, you could give your "Support" for a concept, to support it. Then the names of the supporters where edited into the concept text, and if a concept reached the support of 15 users, it would be moved to the "Concept Collection". The basic idea behind this was that the Edain Team does not need to read the whole thread and just read what the community approved of.
With the upcoming demo we compeltly replaced this system for two main reasons.
The first one was the new English community. Having to gather 15 supporters only to be heard, could really scare of new users, in particular if the English community is really small at that time.
The other more important point was exactly what DieWakküre already stated. The most important thing about a concept is the discussion. It will rarely happen, that everyone agrees completly with a concept, and there often doesn't exist a "finished" version. It happened that people gave their support, if XY is included or excluded in the concept, which made it really confusing. Also, when a concept already reached 10 of 15 supports, it made it much harder to try to improve some aspects, because all the 10 supporters had to give their supports again.
With the new system, we could solve these problems while keeping the basic idea, that it is not necessary to read everything (personally I still read 95% of all concepts and discussions), because the title of a thread allows it to directly see what it is in it, and if the suggestion is worth reading.
Now, why I think that a voting system would be a bad idea.
If a concept is so good, that everyone agrees that is good, it does not need any further support or upvotes.
Else, if there is a discussion with different ideas, just upvoting an idea without giving arguments, won't help at all, because the arguments behind it are the important points.
Please not, that just because a post gets a lot of votes does not make it's content any better or more true, in particular if this vote system is anonymous. That is the reason why such vote systems and polls shouldn't be used to get decissions.