Authorial tract is not authorial avatar.
Yeah pretty much. If you defined every character who says something the author wants to say as an author avatar, I can't think of many pieces of good writing which wouldn't have one. Or twenty. All characters by definition speak things the author intends them to speak, presumably things the author is interested in.
Look, Scotty, the key is that (as NGTM1R would be happy to explain) the author really doesn't come into a piece of fiction once they're done writing it. Unless
the author writes his or herself into the fiction in an intrusive manner, one that doesn't seem to emerge from the story - then that's an authorial mouthpiece.
Kreia doesn't qualify because her beliefs and motivations are completely natural to the story. Without extratextual information there's nothing to suggest any particular motivation to Kreia beyond what's presented in the text. Authorial mouthpieces happen when there's a clear extratextual motivation for the character's beliefs which enter the text - for example, a character in a story raging against taxes on behalf of a political party that doesn't exist in the text, or a John Ringo character who was once a liberal but was converted by the harsh realities of alien invasion and now understands the weakness of liberalism.
This isn't even getting anywhere near
the idea of an author avatar
, which is a character who specifically represents the author in the story. David Weber writes these occasionally. Ironically that TVTropes page does a decent job of explaining what they are, which makes the stupid Kreia quote there all the more mystifying for its total unrelatedness.
Kreia was a complex character in an interesting story but only a drooling TVTropes bottomfeeder could argue she was an authorial avatar. Mouthpiece, you could make a case for (you would lose), but avatar is just silly.