Don't worry about it, that's why Bitcoin mixer exist and anyone can use it to protect their privacy. You can't know the background of the buyer or seller, there's no way to verify it except you're a police that can track his criminal record. It doesn't make sense for us to know who's the person that we send our coins or bought it, no one will reveal his identity and it will make harder to sell our coins if we must know the person.

Just use decentralized exchange e.g. Bisq to skip that and use reputable mixer e.g. Chipmixer.