I will give you one example by Ghostcrawler:
As a rule of thumb, the better posts tend to discuss classes and mechanics and not Blizzard itself. :)
Blizzard wants us to not discuss Blizzard itself on their forums? That is not even in their own long term interest. And especially good are posts about classes and class mechanics?
Sure, as an individual developer you are constantly under pressure to get the small things done. Classes and class mechanics, for example. I can understand that a brilliant idea about class mechanics, written for free into their forum, would help Ghostcrawler more right now than a general idea about what could be improved about, i.e. low-level content.
But that does not mean that the more general ideas should not be discussed. Have a look at this. There are several recent topics about the low-level BGs. Try to find one that hasn't been closed by a moderator for being 'not helpful'. There are none.
Good posters get turned away if only the bad topics are tagged blue. This is basic psychology - don't argue with good posters being irrational. Blizzard, of all people, knows how powerful reward structures are. Why do they ignore them on their own forum?
In addition to that I would like Blizzard to reconsider what posts require locking. Complaining is not always bad. Even if it does not contain any constructive suggestions. It is important, because developers sometimes have a hard time to catch the big picture when they are working on details. (And 80% of forum posters have problems with that every single second).
The complaining about low-level PvP, for example, was necessary. Blizzard shouldn't want it any other way. Among a lot of bad posts, there have also been several very good ones on that topic. Posts that people put a lot of effort in. By closing the topic you also closed their topic!
This is no post about this specific issue, however. World of Warcraft consists not only of the small issues.. Even though these combined are very important, of course.
WoW also consists of philosophies, of directions the game is moving. For example the issue of e-sports during TBC and early WotLK. Back then there were a hell of a lot of posts about all of the sub-aspects of it. For example that a non-despellable 50% mortal strike that applies to all healers at the same time would not be balanceable in arena (without giving it to everybody).
By now Blizzard has long agreed that it was bad idea and I congratulate them. That being said, I also think that Blizzard might have come to that insight earlier if they had tried to answer constructively to well written complains about it. Not just calling it 'QQing' and be done.
Apparently, new forums are introduced soon and I very much hope that Blizzard has an easy mechanism there to tell good posters that they like their posts - without writing a lengthy answer that good posts usually require.
Concluding, I hope that Blizzard will be able to focus more on the good posts there than on the bad ones. 80% of everything is shit. But don't let that keep you from looking at the remaining 20% and always keep reward structures in mind.