So far none of the mentioned places are "improper". At best they might be described as places where you run into more problems than usual. There's a way to waterproof your gun in a baggie that provides excellent access to the trigger. A level 2 retention holster might be preferred when you are going to be doing a lot of moving about, especially if it involves changes from vertical to horizontal and back again.
As Nightmare pointed out, it is improper to carry on the residence/dwelling place of someone who does not want you to. SC law is a bit of overkill because of "some people" who I'm guessing forgot their manners once too often. Thankfully the law does not insist on permission each and every time. Also, complying with the law provides an opportunity to educate someone that LACs are just that as opposed to the crazed killers just waiting to "go off" that anti gun rights folks try to paint them as.
It's probably improper to carry into the room where an MRI machine is, because your gun being sucked up by the magnetic field could damage the machinery. Or is that just imprudent?
I'm not allowed any more to make reference to
http://www.thehighroad.org/archive/index.php/t-19897.html& , but that's just a description of inconvenience, not impropriety.
Seems finding places where it is improper to carry is more difficult than even I thought it would be.
stay safe.