It's understood you can't put a pipe on your mouth or in your mouth before you purchase it. In my opinion, the man bought every pipe he put his lips on. On that score, you have to go by brand and reputation and hope for the best.
When I started smoking pipes in the 80’s, I was encouraged to draw from the pipes before I purchased by the B&M pipe shops that dotted Boston. As a matter of fact, we would look into a mirror as well to see what style of pipe “fit our face” ... Times, and hygiene, have changed. You used to be able to try on various styles of fedoras and caps too, I’m not grossed out.
Normal behavior. Draw testing and pipe cleaner testing are part of the game. If you're going to pay hundreds of dollars for a pipe, you need to know what you're paying for. I would always take sanitizing wipes to the B&M when I would be going for a new pipe.
I'm kind of split on this one. I see both sides. I'm mortified by the idea of someone putting their mouth on a pipe, because after working in the food industry for many years, every part of me screams Ohmygodgross!!! But then I can understand wanting to check the draw or the stem feel of a pipe before spending quite a bit of money on a pipe. If there was some sort of disposable stem covers a B&M could use for such instances it wouldn't fix the problem 100% but might at least help.
Personally, I can’t imagine putting a pipe in my mouth before buying it. If I later found there was a draw issue, I’d expect the retailer to take back the pipe. Also, the retailer would be expected to sanitize such an unsmoked pipe that was returned.