This template can be used by editors as an "expression of embarrassment, frustration, disbelief, disgust, shame or general woe" (see Facepalm) i.e. as a light-hearted mockery, amusement at an unlikely lapse, or humorous disbelief at perceived idiocy, forgetfulness or mistake on another editor's part. However, doing so in reference to the mistakes of others is liable to be regarded as a violation of civility.
Its use as an expression of abuse, mockery, or for the denigration of others is unacceptable. If there is doubt that a recipient would take it in good humor, you should not use it.