Why does eBay allow sellers to change and write their own feedback?

[rspencer9]

Okay, I left a seller negs (rightly so) and somehow, not only were they able to change their negs to positives but they were able to rewrite themselves glowing positive comments from me. How are they able to do this? I tried having eBay call me and I had a1 minute wait, but they failed to call as is always the case with eBay.