An interesting point:
My policy when restoring guns is to black items of furniture that were not case hardened and not to black those that are.
I also hate blacked hammers.
But I do black all levers other than RUL's, as these are always case hardened originally, but I never black hammers and always remove the blacking on those that have been done previously.
The tricky part to decide on is a forend iron that has been previously blacked. Personally, I would not blue this part (as it will have been colour hardened originally) but I have come across a lot that have been. To remove the blacking and have the metal match the action etc is very difficult, either by chemical or mechanical methods, so I usually decide to either leave as is or re-black.
On the subject of pins, I generally temper blue those that are located in un-blacked places and black the others.
I guess its all a matter of personal taste.