Mentioned users may not be reviewers
It used to be that if you were @-mentioned in a comment and came to Reviewable, you'd always be treated as a reviewer: many comments would appear as unreplied, files would be looking for your review marks, etc. This could be an overwhelming experience when you just wanted to reply to the one discussion you were mentioned in.
I changed things so that, absent other indicators, users @-mentioned in anything but the top-level discussion are no longer treated as reviewers. Only the discussions they were mentioned in will be unreplied and they will not be asked to review any files. As soon as they take a reviewer-like action, though — such as marking a file reviewed or starting a new discussion — they'll be treated as full reviewers again.
I expect the new logic to still have false positives and negatives but I'm hoping it'll overall work better than before. Please let me know how it goes!