In regards to your first paragraph: I understand your sentiments, but speaking of "argument from authority" in specific...

I always took this to mean that we can't believe something just because an expert says it. In other words, an expert should be more correct than the guy on the bus, but an argument needs to stand on its own -- it doesn't really matter who says it.

So you wouldn't be flagged for saying the Nobel physicist is more likely to be correct. You would be flagged if you said he is correct because he's a Nobel physicist.

Is my understanding correct? Disclaimer: I've never taken any Philosophy class. :)