I'm not sure this is a downvote. It's a vote in favour of a negative and unlike HN-style downvoting, is tallied separately. You can even react with both thumbs-up and thumbs-down to the same issue.

With a tallied up/downvote system a la HN you can't tell, numerically, if a score of 1 meant "only one person cared" or "hundreds cared and there was furious disagreement".

Actually I'd be interested in a "top 100 most polarising comments" feed :-)