There is a whisper limit in Twitch that I believe cannot be overwritten. Whitelisted or not. The whitelist merely, to the best of my knowledge, keeps the Twitch algorithm that is detecting spam-bots from detecting your bot. The whisper limits are (last I read) 100 per minutes, burst of 3 in a second. The bot that I work on takes this into consideration and internally rate limits the output for that reason. However, Twitch Staff and other developers may know better than I.
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