I would have found it easier to review these Apply HN threads if each applicant had completed the full YC Fellowship application and posted that in their thread as well. For many of the existing threads, there's just not very much to go on, but you have to read each thread before you can work that out. You can feel the inefficiency begin to drag at you as you go through the review process.

Question: Why don't you require all Apply HN applicants to complete the full YCF application, and open those applications to the HN community? Each YCF application includes an option to generate a corresponding Apply HN thread. Comments from the HN community are made available to YC reviewers. The applicant consents to disclosure by ticking the Apply HN box.

Anyone who posted an Apply HN thread could have just lodged their own YCF application anyway, which the YC team would have had to review and determine in the usual way—but completing the application mandates a baseline level of information about the applicant's team and startup. So why not leverage the existing process and help the HN community help you to review them.

Unfortunately none of that will help you choose applicants from among the existing Apply HN threads (sorry), but it might be worth considering for the next stage of the experiment.