GOOD QUESTION:
You do not have to respond to SPAM comments.
I'd say that was the one exception.
I normally do. Sometimes I leave a helpful tip, or a welcome message. Sometimes it's a plea or a warning too, but no, you do not have to engage those comments.
And just in case you haven't had a chance to read through comments, you are also under NO obligation to follow me or anyone else taking part in this challenge. That's not what this is about.
Thank you for the clarification. And I think I was following you already, but if it was a resteem I thinks you're a gem to find! ;)