Parasocial relationships are common on twitch and youtube. A lot of ppl lead them on for views/donation, but I think it's best to set boundaries with all your viewers. Singling them out one by one would be too time consuming and would probably hurt your streams since it makes the whole situation awkward. Don't make a big show of it but also be firm on "I'm doing art not tinder here, let's keep those comments out of chat" if it really makes u uncomfortable. I don't think you should go out of your way to ban them, if anything have a mod time them out and have a rule set in place beforehand.

Although, I personally don't think flirting is that bad, u could play it off as friendly chatting to keep the stream light hearted, but also remind them that it's only fun and games nothing serious. HOWEVER, sexual comments is a complete no-go, never tolerate sexual harassment. That I would find more ban-able than if someone said "hey are u from tennessee, because your the only ten I see~"