And if IDPA wanted it to be prohibited, it would in the rule book as such.
Keep in mind I'm not saying that I'm going to run a retention drill in every match, only that it does have some merit in being included when it comes to defensive pistol shooting and exposes some shooters to something new that is defensive in nature that they may not be able to do elsewhere.
I get that it's a hard topic as there is no standard for it, and that it should be done in very limited circumstances and in as safe a manner as possible (further reading elsewhere shows that a lot of people advocate lowering the target, removing the down zero, and the head as to limit the likelihood of shots going high) but I didn't expect this much hullabaloo over it but it's definitely helping in getting a grasp on what may be too over the top.