I recently signed up for ebay, as in a few months ago, and the signup page has a feature where it'll randomly generate some username options from the real name you entered. I suppose some of them can seem quite random since it tends to add a lot of extra numbers/letters, since there's a lot of ebay users.
For example, the first name I entered was Sunny, and a randomly generated username it gave me was sunsunn_qjqmhc. Sounds pretty random and spambot-ish, but I went with it because I was far too lazy to try and find a username of my own creation that wasn't taken. You're probably just seeing newer ebay users that used the name generator when they signed up!