>> It's not surprising this is flagged. If you read the recommendations, discussions of downvoting (and flagging certainly counts) are not welcome because they're circular, uninteresting, and don't contribute positively to the site content.

This applies to doing so as a response to within comment where the topic itself is NOT the abuse of flagging.

>> Why are only ranked users able to flag? My guess is that after someone invests enough time in HN to accumulate 500 karma

Only 31 rep is required to flag; this is mentioned numerous times already in the comments to this submission.