You've been on Hacker News for over 800 days and have over 300 karma so I'm surprised you don't know this, but... You get a downvote button if you have suffici

You've been on Hacker News for over 800 days and have over 300 karma so I'm surprised you don't know this, but... You get a downvote button if you have sufficient karma (likely 500, since this has been verified in the past and I haven't heard otherwise.) You can verify if you were downvoted based on looking at the points assigned to your own post generally based on if it was greyed out.