Glad someone is at least acknowledging that both parties are acting ridiculous. Granted, the seller has now taken it to a whole other level by getting litigious, but still, both are coming off like giant children.
For whatever reason, either accidental, or deliberate, the postage was short $1.44. Not a big deal. The Med company offered to make it right, but the person left negative feedback over it anyway.
Imagine if this was just an error. To have someone drag your name down even after offering a remedy has got to be beyond frustrating -- especially in an ecosystem like eBay's.