In the past, certain sexual activities among married couples were considered in violation of the Law of Chastity. Now it seems they prefer not to weigh in on such things. I can definitely see the church moving towards a similar "don't ask don't tell" position on masturbation.
That is the de facto position though I myself, who was a youth in the 70's, have never been asked that question.
Look at how the attitude towards birth control has changed over time. It was once compared to murder. Now it's more like drinking caffeine.
While the term "birth control" was used, in that context it always seemed to me to be referring more to selfishly limiting family size rather than actual use of medication and devices though there were some specifics against those as well.
We're informed that the revelation that stated polygamy would never end is invalid because it was never voted on.
Not from any authoritative or doctrinal source.
I'm just wondering when they voted on a masturbation revelation.
There may never have been a vote or revelation. Just inspiration and agreement (noting that Christofferson just told us that unanimity is not the goal). Doesn't change the importance of doctrine though. It is what it is. I believe the more prurient among us unfortunately demand a specific statement on these kinds of subjects and the answer is always going (and must) to be it's wrong because you felt uncomfortable enough to ask.
Consider the fact that some of these answers were found only in the CHI. In other words, only if you asked your Bishop would you find out. Hence, don't ask don't tell.