I'm of the opinion that if a vtuber is experiencing heavy resistance to their chat rules that they should sometimes declare emote only for 10-30 minutes until they're able to cool down. Sometimes making a public display of banning someone can lead to more agitators meaning to upset the streamer. By making chat emote only you essentially calmy, and cooly pasteurize the chat so that you can more easily cultivate what you want from a community while you compose yourself.
Emote only doesn't essentially mute the chat, but it will put a halt to the group of chatters further agitating the streamer.
In the case of Lumi I don't think backseating upsets her half as much as she simply gets fed up after long hours of streaming, and could use more breaks to compose herself. I really think she could use the emote only mode option more often to reduce overstimulation while she tries to digest her meal. I think in general the emote only option is under utilized. I think filian was a shining example in using emote only mode during her chess tournament to not only prevent backseating, but also so that she could efficiently focus on managing the tournament while trying to play chess.
Twitch would not make emote only mode available to streamers if it were a bad thing. I am of the opinion that streamers should try to familiarize themselves with emote only mode, and test if it can be used as a means to have a more comfortable stream. Especially if they are streaaming for long hours while playing frustrating games.
This is just my opinion as a humble 0view streamer though.