Slackbot Custom Response – Multiline Support Explained

Just announced!

Threaded messaging comes to Slack

... Say someone posts a message in Slack that you want to follow up on, but the deeper conversation doesn’t apply to everyone. Now, you can kick off a detailed discussion on that particular topic by hovering over the message and clicking Start a thread. The right sidebar in Slack will open, and you can add your reply.

"Threads" are rolling out "in the next few days". More details at SlackHQ.

While this isn't the most elegant place for feature information, according to this Twitter thread involving SlackHQ, there is no way to limit Slackbot at the channel level.

Edit: this may not suit your needs but there is a Chrome extension for filtering bot messages at the channel level. I haven't tried it so I can't personally vouch for it. If you really need this Slackbot feature then one option is to fork the extension on Github and modify the code so that only certain Slackbot messages are filtered.