Is rice vinegar bad for my non-stick rice cooker?
It should be fine.  The acidity of the vinegar would be an issue if it were to come into contact and react with bare metal.  Non-stick cookware is fine for, say, making tomato sauces, etc, which means the coating in not especially reactive to acidity, which makes rice vinegar okay.

As a confirming point, when I was walking through Costco yesterday, I saw the latest generation of automated rice cooker/food steamer, and it had a sushi rice setting on the new ones, so they are clearly okay for that purpose.