I recently had a post about Different mechanism for votes on questions and votes on answers, Some of the suggested features were repeated but there was a feature which can be considered as novel, so it needs further discussion and a separate proposal.
In the following I propose that feature.
I have tried to make distinct the meaning of votes on questions and votes on answers. Votes on answers can show how well the answer addressed and solved the problem. Since they are candidate answers for one question choosing the better one is also possible.
Votes on questions are somehow ambiguous and opinion based. The number of up-votes may indicate the number of people who have the same questions (In fact they select it as useful). Otherwise, I think when a question has the basic merit of a question, then we can't compare it with another question because they are distinct things.
I might ask a common general question and gain hundreds of up votes, but if I ask a more technical and specialized question few members may vote it up. So, we can't say the former is necessarily better than the later but more common, However, please note that I have no problem with up-votes.
For down-votes on questions the situation is worse and can only imply that the question is not well-stated or lacks the merit of a question, otherwise any question may be searched by somebody and there are some people who have a similar problem.
Also note that since up and down votes on a question have different meanings, a common but bad-written question can still have high up-votes. (Votes don't negate each others)
As I understood, down-votes on questions are mainly used to judge it against the site rules and to notify moderators and OP for the required moderation and modifications. They arr also for the answerers to avoid bad questions to answer.
According to the above arguments, I suggest that if a question already have been established (moderated) and have an accepted answer then down-votes on the question to be restricted because they loose their main function. Please note that I am talking about down-votes and not up-votes, a post can be always voted up.
You may argue that this may lead to a skewed voting system.In fact, a question doesn't need votes (up or down), just an up-vote in that case means add to favorite or how popular a question is.
From a technical viewpoint, an intelligent system can check the votes on the accepted answer, the votes on the question, the time since the question has been asked, the number of modifications and moderations and labels it as an established question. Then it can decrease the effects of down votes or even disable it. Note that if the question really needs a treatment it can be done by moderators yet.
To sum it up there are good answers, bad answers and useful questions for some people. There aren't bad questions but closed ones. Established questions are those which there is no reason to close them.