There is the idea though where each individual could set a price on how much he accepts to get replied to. That might work better as an economic solution.
Interesting idea...a user-configurable squelch...but I can almost guarantee that posts with high value reply settings will get sub-memo'd and the unseen responses will go unaddressed.
Platform can also offer sort threads by value spent. I think trying to use economics (now with bitcoin) is a smart thing to do, to solve an old problem. It's a new dimension.