Buyer uses the threat of a negative feedback as a tool to extort lower shipping fee after the item has already been shipped using the method chosen by the buyer himself. Browsing through his (her?) feedback left for others, it appears that this Ebay user leaves a lot of malicious, negative feedback for sellers.
I shipped the item the *same* day. Buyer didn’t like the shipping method of his own choosing and sent offensive e-mails with personal attacks. My polite e-mails were met with offensive responses that showed that buyer was interested in resolving the issue but to pursue the agenda of getting the already-purchased item for less than the final auction value. I refunded the full amount the same day he complained about “long and expensive” shipping (that was chosen by him and precisely calculated by UPS). I lost money and gained nasty negative feedback thanks to this unpredictable and malicious buyer.