How are they lost?
Good insight -> becomes balance change -> is a part of FAF
In addition, the team itself isn't some committee set up by the Balance Councillor but rather more of an association in itself. This means that there are always old dudes around that can say why certain things were ignored/discarded/whatever to the newer members that get recruited. Not to mention having the game competency to recognize insights independently is kind of expected of someone joining the team.
The forum would just serve as another thing for dudes to read, digest, and ignore because their cheese got nerfed and they don't really care about the 1000 pages of reasoning you wrote explaining the necessity for it (almost like people already do that on the balance forums). Same as people do for current patchnotes with their synopsis and same as people do in every balance patch release thread.
I mean the real solution here is active/heavy-handed moderation of the forum so things going in circles stop in their tracks. That's all that's really necessary.