Definitions And Mary Sues

Some definitions are massively helpful. People complain about the need to define every little thing, but I personally enjoy defining things, because if you removed every label from your vocabulary, you could not speak. Language is built around definitions and labels, and you cannot discuss something that is ineffable. 
What I dislike is when labels are in some way inaccurate, or unhelpful. I recently read an elegant definition of ‘comics’ (in comic form, no less), that not only summed up what a comic is, but was very affirming and encouraging with it- encouraging readers to  reexamine, expand and ultimately redefine ‘comics’. 
The term ‘Mary Sue’ is not helpful, accurate, or encouraging. It is not well defined (come at me with your definitions, and I will turn every one of them away (examples are not definitions, by the way)), it is discouraging (tell me that you have never taken one of those Mary Sue tests with a character and felt like absolute shit when your character scored poorly) and they actually hinder helpful dialogue and discussion (“What’s wrong with my character?” “Oh, she’s a total Mary Sue?” “What’s a Sue? Why is my character one? How do I fix that? Is it even a bad thing?” “Idk, google.”). 
‘Mary Sue’ is an emotional rather than analytical judgement. While the emotions are really important (check out I Am Sue, which is in the typing right now), it’s not enough feedback to tell someone that their character is a Sue.