would also like to see your explanation for when it's inappropriate to apply reason

It is inappropriate -- well, let us say it is a mistake in reasoning -- to apply reason to something whenever it is obvious that the time and mental energy are better applied to something else.

Interesting, I had in mind something much stronger. For example, if you attempt to apply too much reasoning to a Schelling point, you'll discover that the Schelling point's location was ultimately arbitrary and greatly weaken it in the process.

Another related example, is that you shouldn't attempt to (re)create hermeneutic truths/traditions from first principals. You won't be able to create a system that will work in practice, but might falsely convince yourself that you have.