My understanding is that the "appeal to authority fallacy" is specifically about appealing to irrelevant authorities. Quoting a physicist on their opinion about a physics question within their area of expertise would make an excellent non-fallacious argument. On the other hand, appealing to the opinion of say, a politician or CEO about a physics question would be a classic example of the appeal to authority fallacy. Such people's opinions would represent expert evidence in their fields of expertise, but not outside them.
I don't think the poster's description makes this clear and it really does suggest that any appeal to authority at all is a logical fallacy.
I agree the poster is wrong. Appeals to authority can also be non-fallacious but of very weak inductive strength: for example, when the authority holds the minority opinion for her field. They are also fallacious as deductive arguments.
http://www.yourlogicalfallacyis.com
Just printed an A3 of this.
See now http://lesswrong.com/lw/c9u/logical_fallacies_poster_a_lesswrong_adaptation/