First of all, I sympathize with the OP: seeing
-15 unaccept stings a little. Umpire signals a home run, you circle the bases, and then they rule it a ground-rule double after review. Would feel much better to have a double to begin with.
That said, I think un-accepts are merely a symptom of a deeper problem: fragmentation of knowledge between a large number of relatively short answers. A questioner, like an inexperienced driver, would benefit more from thorough directions of one person than from multiple quick suggestions given by a group of well-meaning backseat drivers.
I hold the view that the active sorting of questions is no longer suitable for Math.SE. It's fine for slow-moving sites where active developments should be emphasized. When the site is already like a bustling city, such emphasis on activity leads to some questions becoming hyperactive. They honestly look like a riot in the city. The site ends up with oversupply of similar answers at some places, and their lack at many others — hardly an optimal state.