YC/HN is for startups. You don't need to wait for permission to do something. If you want to nominate someone great, I would just email that person to encourage them to apply. Done.
I understand that, and if this was a normal application for its standard incubator, I'd understand. I read this as seeking out people doing exceptional work but aren't _already_ being noticed. A lot of this people might not be noticed because they aren't trying to be noticed, but may very well benefit from it, or they don't have the means to / maybe they were never pushed to put themselves out there. Encouraging application is certainly a good way to go.
YC/HN is for startups. You don't need to wait for permission to do something. If you want to nominate someone great, I would just email that person to encourage them to apply. Done.