I've been downvoted because HN has Dislike Button which encourages people to downvote things they personally don't like instead of making constructive arguments ;)
If it's any consolation I did provide a counterargument and got downvoted for it.
As for the 'flag', that's not the same as downvoting. Or at least shouldn't be used in the same way although I have lately seen a disappointing number of comments marked as "flagged" which shouldn't have been. (There's some guidance about flagging posts here: https://news.ycombinator.com/newsguidelines.html). Downvoting is something that's only available to members above a specific karma threshold (2000 IIRC).
As for the 'flag', that's not the same as downvoting. Or at least shouldn't be used in the same way although I have lately seen a disappointing number of comments marked as "flagged" which shouldn't have been. (There's some guidance about flagging posts here: https://news.ycombinator.com/newsguidelines.html). Downvoting is something that's only available to members above a specific karma threshold (2000 IIRC).