I'm really pressed for time, so this will be less word-crafted than I usually try.

    If you'd like to filter on stories with those words
    in the title, you can use the "title:" operator:

This seems completely unobvious.

    Did you try sending us an email with your feature
    requests?

No, because I tried using several combinations of the obvious things to try, got frustrated, and honestly couldn't bring myself to care. I know that's going to be frustrating to you, because no doubt you do care and want me to care as well, but I'm finding that whereas with SearchYC I could find pretty much anything I wanted really quickly, with HNSearch I simply can't. It returns stuff that seems irrelevant, or not what I wanted, and doesn't find the stuff I think it should.

And I'm too old, too tired, and too grumpy to try to work out why. In particular:

    ... you can use the "title:" operator:

... just seems like too much hard work.

So good luck, hope it works, but I'm probably not going to provide much high-quality feedback.