I do not post, so my karma must be non-existent.

It's 501, it's right there in the top right and in your profile page.

Your karma is in the top right. You need around 300 to downvote, 800 to flag. Your downvote by clicking the down arrow beside every comment and submission.

I just logged in, saw my Karma, and just got the double arrows... I did not have that before... I have downvote for posts, but not for comments. ( hence, I cannot downvote your comment. )

Down vote comment. Nope, only 1 arrow for up, and I am good with that.

Just refreshed, and now I can down vote some comments...

Refresh again... I cannot down vote posts, but can down vote even less comments... someone is watching, and laughing at this. :P

If you can downvote any comment, then you've got downvote powers.

You cannot downvote direct replies to your own comments though if that helps understanding what might be happening here.

There's a time window for downvoting, once it has expired nobody can do it. I don't remember what the period is, maybe 12 hours.

The thresholds were a guess tbh. Glad you got your downvote powers :)

You can't downvote replies to your comments and in other circumstances I think.

Downvoting is not supported for posts--only for comments. Once you have the power to flag, that is the option.

Apparently the minimum karma to downvote is 501: https://github.com/minimaxir/hacker-news-undocumented?tab=re...

I recently got to 300 and I saw no change in the UI.