User flags on submissions do affect rankings. If a submission receives enough flags, the [flagged] tag will also be displayed. You're right that there isn't a w

User flags on submissions do affect rankings. If a submission receives enough flags, the [flagged] tag will also be displayed. You're right that there isn't a way for non-mods to know exactly how many flags a submission has received. There are some other knobs the mods can turn, but user flags definitely are used and useful. If you see something you feel is inappropriate for HN, flag it. Community curation is definitely a part of HN. I have seen the mods override user flags for contentious yet popular submissions, but that's been rare, in my experience.