I for one don't know who this Mary Sue is, but know of Luna and Homestuck (which I ceased to read pretty early).

I read them like many webcomics, as an easy read that cares too much about continuity for being able to see that when you need three pages of explanation to justify the logic behind an action, it's worse than a retcon. I mean I've never read anything approaching it in good comics nor in good books: you don't see Shakespeare explaining how Polonius gets killed in one movement, or Hugo saying how much weight Jean Valjean lifts daily at age 50 to be able to lift a horse cart, or Schnitzler calculating the time it takes to go from Prater to the opera... It doesn't matter, because even if you recognize the irrealism here and there, it's not a scientific treaty about swordfight, weightlifting or best Vienna routes, the rest is enough to make you yield a certain sum of disbelief...

And the problem with QC today, it's that the rest is not enough to fill a second zone newspaper syndication. It's silly, but not to the point to make it pythonily humorous. Quips are rare and screwball is gone. It's gone from a funny timekiller to a timely funkiller.