Sometimes a streamer just bans a person in chat, but sometimes they talk to them first.

It can be confusing to know who they are talking to. Chances are the streamer or the mods likely clicked on the person's username of the person they are not having a good time interacting with.

That clicking action could cause the words [USER YOU BLOCKED] simply in the first instance of that troll in the chat, where the streamer or mod clicked.

Now any interactions by the other chatters with the troll will be more obvious. And you will not be looking for the chat interactions because you will have likely found the cause.