We've just deployed an improvement disabling prefixed search when the query comes from the news.ycombinator.com or after form submitting (press enter). What do you think?

Better, but you need to stop ranking by points and switch to a relevance metric. There are two main issues right now: A lost of the posts are really old, and the results are plain bad. Here's some results I get when I search for "Go" again:

1. Reddit to go dark on Jan 18 to protest SOPA 2. Go Daddy No Longer Supports SOPA 3. Why we can't go back to business as usual post-PRISM 4. Right click and save as needs to go away

and so on. You could for example, instead of just maching a single keyword, look at the post contents and comments, and see if that keyword appears multiple times. A discussion about Golang is bound to have more entries of "Go" than "Go Daddy no longer supports SOPA".