Sometimes AKA the "Forum Whiners" effect, well known in the PC games domain:

When new PC games are released, almost inevitably the main forums for the game will become flooded with a large surge of complaints, negative reviews, rage, rants, and other negative stuff. This is fully expected and the absence of such is actually a bad sign. People that are happy with the product are playing the game, not wasting their time looking for forums and posting comments there - while people who have a problem or are really unhappy often look for an outlet or a solution to their issues (though the former in much greater numbers, usually). If no one is bothering to post on the forums, then that's evidence that no one cares about the game in the first place.

I see a lot of similarities here, so perhaps that's one thing worth looking into? I'd expect some people somewhere to have done the math already on this feedback (possibly by comparing to overall sales, survey results and propagation data), though I may be overestimating the mathematical propensity of the people involved.

Regarding the stop-watching-threads thing, I've noticed that I pretty much always stop paying attention to a thread once I've gotten the information I wanted out of it, and will only come back to it if someone directly replies to one of my comments (since it shows up in the inbox). This has probably been suggested before, but maybe a "watchlist" to mark some threads to show up new comments visibly somewhere and/or a way to have grandchildren comments to one of your own show up somehow could help? I often miss it when someone replies to a reply to my comment.