Perhaps you didn't get me.
If it gets initiated by category tags, it's super easy to use for the user whenever it's required. But then what's the solution when one don't want to initiate it yet he/she wants to use category tag in his comment? Shouldn't a special tag to not to activate the bot is required there?

Well, whatever you think is good, you just go ahead with it. I was just giving my piece of mind. You know your bot and its audience better. I ain't into coding.
All the best to your project!