Why hasn't Yahoo banned the account 's IP Address who is posting the aposties and apostates rant/question in this section?

The following is an answer to that exact question from the Yahoo Answers Team several years ago. I doubt the answer has changed since then.

One IP address can belong to thousands of users. So punishing one user will actually punish a lot of innocent ones. Also in this day & age of proxies and dynamic IP addresses then it rarely works on other sites either anymore. If one IP address is banned today then another will be used tomorrow. We try other tools, but the banning of IP addresses is not an effective option.

There is no reason not to let these questions stay. Someone doesn't like them so they are able to delete them. That troll doesn't have the power to get him banned.

aPOSties and ApoSTATes troll is ultra annoying, but they won't even delete that user.