Quad9 is fine. Don't let that user scare you. Here's a quote from Quad9's own privacy policy section regarding data sales:
2.3 Sharing of data
Quad9 does not share, sell, or rent any information that could identify an individual.
We do not share this information because we do not have this information. We do not have this information because we do not need this information. Because we do not need this information, we have built no mechanism to collect, retain, analyze, or distribute it.