If you think someone is a bit of a local celebrity on HN, you can click the domain name on a story like this and see what their blog was submitted for. Usually useful information.
I fat finger downvoted you. Here's my verbal upvote.
This was news to me, thanks.
These days there's an "unvote" text link added next to their name, or "undown" for the case of a downvote.
In addition, on my mobile, when I accidentally or intentionally hit the downvote, it doesn't take the first couple of times. This has saved me numerous unintentional downvotes. Thanks, HN!