If you think the submission is inappropriate for HN, flag it and move on. Or if you're new to HN, take some time to get to know the community and its behavior. You may want to review the guidelines again, which mentions refraining from commenting that submissions are inappropriate, as well as avoiding gratuitous negativity.
If you have enough karma, you'll see a "flag" link under the submission title. I think the threshold is 20, (so you'd need 21) though I may be mistaken.
As you're new, I'd be hesitant to flag too many submissions, even after you have enough karma. Take the time to get to know the community more, and its standards.