This page in a nutshell: While they are allowed use of the shovel, who are we to say where they might dig?
Editors are permitted, providing they otherwise stay within the guidelines, policies and rules of Wikipedia, to commit to record their various misjudgements, misunderstandings, misapplication of policy, mistakes and general misdemeanour's when not in article space. While third parties are welcome to point out any or all shortcomings, it should not be in such a manner as to deny the editor from compounding the error if they so wish. This privilege is re-inforced by repeated (mis)use; the more determinedly a poor choice of course is pursued, the more the chooser is permitted to follow it – so that it may lead to its logical conclusion. This does not disallow good faith attempts to deflect of dissuade the embarkee upon the journey, but only so far as civility and respect permits.