What would a solution in surfacing good chat messages from Video Live Chats look like?

Good messages create conversation, and good conversations are a source of knowledge for the whole community.

Knowing that, why isn't any of the big social platforms allowing for live chat message replies on Video Live Streams? (I'm talking here at YouTube / YouTube Gaming / Twitch / Facebook)

They allow replies after the Live Chat has ended in form of comments (Top Comments on Facebook / Comments on YouTube)

What's the logic behind not allowing replies on chats during the live videos? And how can one go in surfacing good comments from Video Live Chats?