Earlier quoted context omitted.
If instead of showing up at my door I got a note that said you need to come down to the post office during business hours and pick up your package and bring an extra $1.44, I'd actually be kinda put out. This was a mistake by the shipper for mis-weighing the package (as they note in the feedback "This has happened alot from USPS lately." - maybe they need to get themselves a new scale) it should get negative feedback…
Right. This was an intentional attempt to cheat the system that the seller fails at, repeatedly. They attempted to screw the USPS and the customer got the bad end of their incompetence.
You don't know that. Say the seller has a faulty scale and does large numbers of transactions at once. 100 packages go out, and 100 postage due complaints come in.
Oops. Clearly the seller is a scumbag.