That would penalize threads that were so interesting that you would want to read the comments there multiple times, and even revisit them in the future.
Generally it’d be a bad metric if it encouraged you not to revisit the threads you liked because you didn’t want to lower their score.
The site already (approximately) tracks which users have seen which comments, so it’s probably feasible to track the number of users who have seen a particular comment.
That would penalize threads that were so interesting that you would want to read the comments there multiple times, and even revisit them in the future.
Generally it’d be a bad metric if it encouraged you not to revisit the threads you liked because you didn’t want to lower their score.
Is it not possible to track unique visitors?
The site already (approximately) tracks which users have seen which comments, so it’s probably feasible to track the number of users who have seen a particular comment.