TV Trope's neologisms aren't useful in literary analysis since they have no generally accepted meaning outside of internet hipsterism. They're are fun to read though.
Okay, this is just too funny. You realize you're talking about the term "Mary Sue," right? It comes from Star Trek fanfic! It's on
exactly the same level as TvTropes. It's not like you can break out the Oxford English Dictionary and point to the definition. And "literary analysis?" If this thread is literary analysis, then TvTropes is a freakin' dissertation. Which is actually not so far from the truth; academic literary analysis is mostly just TvTropes with bigger words and more pretensions.
If you want a discussion of the Mary Sue concept and its applicability to both fanfic and canon characters (and no, the fanfic community does not have exclusive rights to the term), TvTropes is an excellent place to start.
My own personal definition:
Mary Sue is any character whose presence causes reality to lose all depth and become a mirror reflecting her glory. All sympathetic characters love and praise her, even if they ought by rights to hate her guts. (They may turn against her briefly, so that the universe can then show them the error of their ways.) People who would normally step up to solve a problem simply wring their hands in despair, so that Mary Sue can save the day. All desirable characters want to sleep with her and/or are in love with her, regardless of whether this makes any sense for those characters. Everything she does is the right thing to do, and all the other characters agree that it was the right thing, even when she does something that in a non-warped reality would be considered appalling. The only time she's ever wrong is when she has doubts as to how special she is.
Is it always a bad thing for a character to be a Mary Sue? Well, I hesitate to say
always about anything, but almost always, yes. Is her presence proof that the writer sucks overall? No. Good writers, even great ones, sometimes fall into the Mary Sue trap while remaining good writers in other respects. IMO, Buffy the Vampire Slayer became textbook Mary Sue in the latter half of Season 7, and she had some Sue-ish traits going on before that. I'm not fond of that part of Buffydom, but I still love the show overall and think Joss Whedon is an awesome writer.
I honestly can't say whether Elminster qualifies, since I haven't read the novels in which he plays a role. From what I've heard, he certainly seems to have some of the traits, but maybe it's exaggerated.
Oh, and regarding the "nudity is non-sexual in the Realms" business: Again, I haven't read the novels, but based on past experience with this sort of thing, I am extremely skeptical. If there are examples of this lack-of-nudity-taboo where the non-Elminster participant is
not a stunningly attractive woman, I'll believe it. Otherwise, it's just a thinly veiled excuse to have stunningly attractive women get naked around Elminster.