Most of my orders for comic TPBs and larger come in brown solid envelopes, but I get some smaller paperbacks in padded envelopes. They still arrive fine to my satisfaction.
I'd recommend buying in a store if it's a big concern.
Any sort of postage/shipping has the risk of hardcover corners being slightly bent. Bookdepository.com has sent me hardcovers with some slight rounding on the corner.. Amazon.com has me hardcovers where the dust jacket was torn. I know what I prefer out of those two.