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This is based on an engagement challenge, the contest of the week, from a specific community.
It is also unique engagements therefor not a comment on a comment. It will thus be comments to different people.
Comments will also not stop at 30. We still take in account the number of comments plus the quality thereof and the quality of the posts.

I try to understand what you explain...
Just leaving a comment and never return doesn't sound like engaging to me but I can be mistaken.

I wish there was an option to block these people.

Let's just help them where we can. (•ิ‿•ิ)