If one of my kegs had a pinhole I would certainly try to solder it. What's 30 PSI amount to on a tiny hole with a diameter of 1/64"? I might only use it for storing StarSan to purge other kegs, etc, but that tiny hole sees very little pressure in a homebrew situation. If the soldering job turned out really well I certainly would put it back in beer service.
OTOH, the question about bleach damage is a good one, if that were the cause it's likely it will spring several more pinhole leaks. In that case I would strip it down and scrap it.
If you leave 100% bleach in a keg for a few days, you will end up with a pinhole right at the exact spot shown in post #1. Then, when filled with beer, it will slowly leak into the rubber seal, and you end up with 5g of beer on the floor of your keezer. Then you scratch your head many times because you can't figure out how it's leaking until you you cut away the rubber. Ask me how I know In my case, keg got recycled. In the case of an unscrupulous person, it might end up on craigslist and become a problem for somebody else (which is likely what happened here).
I agree that that the hole size means the solder or other fix won't likely fail. Minor correction to what was posted above: the hole will see the same pressure as the rest of the tank (i.e., 30 psi). But the force is less (force = psi*area).