The following post was from the Gaia writing forum and it highlights some common problems with Mary Sues. Minor edits.
Zract
Okay, let's start with the Mary-Sue/Stu writers.
Note: These fics are about as interesting as a log rotting
Mary-Sues:
Do you honestly think that writing your own graceful, hidden-powered, mysterious, hyper, strong girl, who usually either ends up saving the world with the main character by sacrificing something is actually appealing? To some morons, it may be, but, to us long-term writers, we know better.
Sometimes the girl is overly hyper, or maybe cold... and some of you have about as much sense as a stick to make her a cold, heartless girl with a confusing past, and then throw her into story-telling scene where she tells her tale about how she lost her family in a tragic accident/murder/raid by bandits or worse yet a big fire.
This is brimming with originality. It helps that the character is always, ALWAYS graceful and moves fluently.
Oh, did I mention that her name is an American name, even though most fanfictions are based in... OH MY hamGAWD! JAPAN?! Who wouldda thought it!?
🧝♀️Not true. There is life and fiction beyond anime, people, take a hint.
There are many people in America with non-American names too. So it goes. There are stereotypical names overused in fan fiction that are decidedly non-American, or a strange spelling of a familiar name, or a name that's supposed to have some sort of meaning concerning the character. All can be overdone and annoying.
The name should be something the writer likes for the character or else it just doesn't work.
so don't get stuck on the name thing too much.
Moving on...
👩💻Then, the next day, the hottest guys is mysteriously nice to her and COMPLETELY out of character. Of course, it's probably then that the female characters are either the best of friends with her or complete wenches filled with jealousy.
She saves the world, sacrificing something dear, sometimes her life (and of course, most of the story goes on about how brave she was and how she would never be forgotten for her bravery when she dies... blah blah...), but if she lives, then she is paired up with the author's ideal guy.
The character, and the plot should be put in an ittsy-bittsy-yellow-poka-dot-bikkini (mostly because it is the most embarrassing thing you could ever wear when you DIE!) and shot.
Marty-Stus
🧝♀️Agh! Gary Stus. Sorry, but another article that refers to them as "Marty Stu"s is irritating.
👩💻These should be shot -of course, ittsy-bittsy-yellow-poka-dot-bikkini included.
Now, what part do these guys play?
Well... usually, it's about some guys with weird powers, if not someone to make another guy jealous or is a side love story with a female character include *accesories and all...*
But still... the character has a mysterious past, no? Solution... stop writing the dang fic...
🧝♀️Yeah, especially when that past is about that character having a connection to hell - like the devil is his father and he has a demon pet wolf etc.
👩💻You try to fit Japanese into an ENGLISH fic
🧝♀️That's just anime fanfics written by otaku. Not the case with other pics.
👩💻There are some talented writers out there, full of potential and greatness that will come to them later on it life... as soon as they realize that the Japanese language doesn't belong in an English fic. You do not see people adding tomato juice to a glass of orange juice and drinking it. It tastes bad just as the Japanese term "Gomen ni sai" is thrust into the fic. And so it crumbles like a sculpture being smashed to bits.
🧝♀️Couldn't have put that better myself.
👩💻Most of the time when this happens the translation is put at the top of the page or the bottom, and sometimes, not at all.
🧝♀️Which doesn't work either way. Who, other than an otaku is even going to care?
👩💻Do you people go up to an English-speaking person and start speaking Japanese, or is this stupidity just a natural talent?
🧝♀️*Applauds* Good question. Wouldn't surprise me.