SWM wrote:No, it has not been retconned out of existence. It still exists, and it still has the shortcomings that were identified in On Basilisk Station.
The problem is that people keep thinking they have come up with some way to get around those shortcomings. David had hinted early on that it would reappear (possibly modified?) in the books, but he (and everyone else) got so tired of hearing yet another "brilliant" and "original" idea of how to use it that it became known as the Weapon That Shall Not Be Named. At this point, it is not clear whether David will bring it back in the books again; but the weapon, it's use against the Sirius, and it's problems are still canonical.
And don´t we all wish fervently that everyone could remember that those problems exist!