I just got a notice I supposedly breached TOS from an old answer, why?

Several points. They now say TOS, even if just a Guidelines violation. No, nobody reads it as removals are software based using the reports from different users. They have NEVER said what was wrong as a part of notifications the last few years. There is no way to do that. The fact you do not give the context of the Q&A is usually telling. If you want to know the reason for the violation, post "Why was this question (answer) a violation?" and add the original e-mail you got so the users can see the exact context. The experienced users here will explain it to you.

It isnt yahoo that reports posts. It is users on this site known as "Trusted Reporters". As you can see, some of these reporters cant help themselves when it comes to reporting someones post, no matter how old the post might be... or how mild the violation might be. Instead of getting mad at users that have to live with such an OCD mindset, we should feel sorry for them. Maybe even pray for them if youre into that.

There are some people in yahoo answers has good track records. When they raise a complaint and even though there is nothing wrong about that, the content will be removed. This is unfortunate.