Whispers are (rightfully) strongly restricted for bots. But being able to respond to whispers sent to the bot would allow for a wide range of applications while not opening anyone up to spam (who is not seeking it).

Use case 1:
Many streamers use commands to answer repeating questions. The commands and their output are however only usefull to one user (who is using the command). For everyone else it is only filling the chat with extra messages that might make them miss something.
Another scenario: when playing minigames via the chat, the chat can get verry crammed with commands and replies, very fast, making it hard for streamers to read all the non-command/answer messages. If users could send commands via whisper and get the answers there all that spam could be avoided.

Use case 2:
Giving out secret roles, code words, etc.: Answering to whispers would allow a streamer to give out user specific information in a secret manner - usefull for all kinds of minigames or community events.

Use case 3:
I am a bot, please ask one of the human mods. Ok. Personal gripe here. My bot gets waaaay too many whispers with questions because people don't realize it's a bot. Being able to let them know that they are not going to get an answer here would just be nice.

In conclusion: the ability to respond to a whisper for all bots would open up a lot of fun & usefull interactions between a streamer and their community without compromising anyones safety.

tl;dr feature: Up on recieving a whisper, a bot of any verification level can reply with one (1) whisper message back.