Another reason to not hang a bear can is that about the one way a bear can get into a bear canister is if it drops from a sufficient height to crack the plastic.

In terms of odor, to reduce odds of a bear visit, a person can use an odor proof aloksak inside the can. I think most don't; I tend to use one with an Ursack but not an actual bear canister.

The amount of scent that escapes from a can --- and whether or not ants can crawl into it --- depends on the type/brand. The threaded screw-on cap of a Bearvault model isn't going to allow ants to crawl in. It's certainly not odor proof, but I would guess that it's more so than the older black plastic Garcia type.