A user downmod is when someone pushes the "upside down triangle" next to a person's name and/or point score for a particular post, or, in some other way decrements a person's "karma".
When downmods serve to censor my content, they become my business. I don't know where you pulled 'upvote' from, though; I'm not sure there is much value in knowing them.
Edit: Someone is getting a feed of something...or they are just furiously refreshing this thread. hehe
https://blog.ycombinator.com/two-hn-announcements