Depends on the kind of damage I suppose

Depends entirely on damage and packaging. Outer packaging that's just ablative armor? It's fine. Packaging was torn a bit but the food is safe being exposed to the elements (like bread or crackers) fine maybe. Food that needs to be packaged to be safe at room temperature? Noooo.

When I'm stocking shelves (yay) if the box is damaged, but the product isn't exposed to air, I'll damage it out and add it to the donations pile.

If the product is touching air when it's not supposed to, pasta is the exception since it's pretty much always exposed, it gets damaged out and added to the compost pile

No I do not eat food where the packaging is damaged.

Trust me, dont do it.

As long as the contents aren't damaged, countable contents aren't missing any, and bagged contents are airsealed, I'll keep it. If it's potato chips, I'll eat them immediately if not stale. If, like one time, it's a rigid tub of icecream, and the icecream has a groove by the hole consistent with melting and pouring out, and black dirt particles inside, I'll return it. Look, shopping can be stressful and I've missed some ridiculous things

Really depends on how damaged. I once bought a tub of Ben and Jerry's from a local shop (interestingly and unrelated also a drug front), got home and noticed the plastic film wasn't wrapped around to secure the lid. Thought nothing of it, opened it and someone had eaten a mouth full of it and must have put it back on the shelf. Doubt they were carrying a spoon with them so can only assumed they scooped it out with their hands. Put me off ice cream for awhile

Depends on what kind of food, how it's stored, does it smell funny?

I'm unlikely to try to replace it once it has made it's way home. Not worth my time.

Unless it's pierced/open ... of course. Why wouldn't you?

I have no hard and fast rule for this, it really depends. Some things are a hard no, others I play fast and loose with.

If it smell bad or have fungus I'm not eating it, if don't probably yes.