I have had an epiphany:
Ebony Dark'ness Dementia Raven Way is not a Mary Sue.

Hear me out for a moment.  When a person says that Enovy, or any character, is a Mary Sue, they are making the implicit assumption that a character can be a Mary Sue, and therefore that being a Mary Sue is a characterization issue.
It's a reasonable assumption to make.  After, all of these characters tend to have a lot of things is common.  They're practically perfect in every way.
"Practically perfect in every way?" That sounds familiar, doesn't it?  Mary Poppins does have a lot of common Sue traits, doesn't she?  So how come no one ever calls her a Sue? Or Superman? Or The Doctor?
On the other side of the issue, how come when writers try to give their characters flaws, they only make the problem worse?

It's because Mary Suedom isn't a characterization issue.  I contend that a sufficiently skilled writer could make an compelling story about Ebony, or any Mary Sue character.  A poor writer could, and often does, turn otherwise good characters into Sues.
Mary Suedom is a writing issue.  It's a problem that occurs when a writer is unable to get the reader to care about a character, and tries to force them to care by adding fluff.  That's why when they add flaws, the problem gets worse.  They aren't using the flaws to give you insight into the character, or to make them relatable.  The flaws are just more fluff for them.
That's also why a well written character often won't seem like a Mary Sue, even though they could check practically every box in a Mary Sue trait list.  It's because the author can get you to be interested in the character.  They not only show you what the character wants, but why they want it, and how far they are willing to go to get it.

A character is enjoyable not because of what they can do, but because the reader cares what happens to them.  The reader wants to see them succeeded or fail, and they want to see how the character handles the problems that occur along the way.
If the author can't get the reader to care about a character, no amount or changes to their appearance, special powers, or angsty background is going to change that.
But if the author can get the reader to care, the fact that the character has blue hair, seven katanas, a pet dragon, and a stupid name, isn't going to negate that.