So a mining pool isn't allowed to go into a coin's thread and mention that they've added that coin?
No.
If you'd like to send a personal message to the OP then you can do, maybe if they deem it appropriate they may add it into their announcement that you can mine at x pool. Other than that its not allowed, and a lot of the owners of these announcements actually report these sorts of posts.
Are you actually saying that you would ban people on the word of the original Bitconnect devs? Please confirm.
Isn't there a feature called "self-moderated thread" if the OP doesn't want people to have any freedom in their topic?
If the OP didn't choose self-moderation, why would he have any more authority than me over what people are allowed to say in the topic?