To me, "flag" means "this is a serious violation that requires moderator attention". Something I'd want you to see and deal with because it's bigoted, illegal, spam, etc. I wouldn't flag something simply because I didn't think HN was the right audience, or because I personally dislike the topic. You seem to be encouraging me to use it simply as a downvote.
I'm not going to start flagging things, nor do I feel that strongly about the lack of a downvote, but if flags are effectively downvotes behind the scenes, and if that's how users are treating flags (which they obviously are, from other comments on this thread), I think the UI should have a downvote button.
I assume there's been discussion about this before and I'm curious about the thought process behind the decision. I don't find the FAQ to be informative about this.
He must have been thinking something though, because Reddit was originally his conception and he was an influence on the earliest development of Reddit as well (edit: and Reddit does have story downvoting - forgot to mention that bit).
The one exception is if some group organizes to upvote something that fits their agenda / business plan. But in this case it's generally something worth flagging and it gets flagged?
I never flag anything because it's recorded on my profile, and I don't want stuff recorded on my profile that isn't useful to me. I only upvote submissions and comments that I intend to refer back to in the future. Upvotes are simply bookmarks to me, so my only tool for voting on the quality of conversation is downvotes. Which, apparently, I can't do for articles without spamming up my profile.
Actually I just checked my profile and saw several flags that must have appeared on a mis-click, just like how sometimes upvotes appear on a mis-click. Fortunately, unlike mis-clicked upvotes, you can still remove these.
Thank you for your tireless work. HN is a breath of fresh air compared with the rest of the internet thanks to it.