q. on bike mechanics / placement of front derailleur

[madisongrrl]

He also said that rubbing the chain against the bottom of the derailleur cage, while annoying, is not damaging to the components, just noisy.

This is unacceptable.....especially if you are in a reasonable gear (not cross chained)

My discontent is compounded by the fact that the new bike feels so darn short. I am fairly sure that is just because my old bike had such a ridiculously long wheel base for me.

Did you get a bike fit?

Intellectually I know that this just means I need to learn to get further back behind the seat while descending, but there is still this niggling "what if this bike is wroooong for me?" feeling.

If it's wrong, you'll be buying a new frame and swapping the components. Take this bike back to the shop and if you don't get satisfaction, take it somewhere else. You'll have to pay, but another shop's opinion is worth it.