EDIT: Sorry for the misunderstanding: as mentioned elsewhere, the problem is not so much the user-agent end, but the hops between where the decryption happens and where the information is used. Why expose the information more than needed there? So I guess ebay's response is a bit lacking. They could make things more secure with relatively little effort.
Except that ebay's response was to the POST over https he mentions in the first section of his article. There is absolutely nothing at all suspicious about that. He wasn't looking into a potential security hole there, he was just prodding as to why they do server-side validation in a completely secure manner. His email had nothing to do with security; he was wasting someone's time asking about implementation details.
He then went on to find a GET version in another area on the site, for which he makes no mention of having sent an email. This might not be considered a security problem to ebay depending how they manage web server logs, but it's certainly a viable inquiry compared to the POST version he did email about.
In general though, yeah, not that exciting of an article.
It's completely unnecessary to have everyone's passwords be viewable by however many people have access to one or more of those logs (for a org the size of ebay, maybe 10-100 people?).
Sure, it's not as terrible as if it was sent over http, but 'not being as the worst it could possibly be' isn't a very high bar.
So someone getting access to the logs will have access to a lot of possibly sensitive data, that's all depending on server and application settings, but by default GET are more likely to leave traces than POST.
It's a subtle but valid concern.
Bad content: when you log in or register you send your password to the servers anyway. It's irrelevant, since all connections (as shown in your post) are made with https.
One could argue "they are seeing what you write even if you haven't sent it yet", but meh, it's just a damn password field, not a chat field.
So bad, bad, bad.