Require verification to follow a channel.
Over the past couple years on twitch a person, or group of people have been DOXing me constantly using their usernames to do it. I think the best way to deal with this is use the email and phone verification and allow streamers the ability to have verification as a requirement for following. I would specifically go with phone number myself.
This has again been going on for years and twitch has been no help when reaching out to them to stop this from happening.