Experience with curating content. That includes:
- looking for authors all over the chain (by using different tools and methods)
- judging quality (still subjective but experienced curators have higher standards I guess)
- and investigating to check for plagiarism/identity theft (which is a hard thing to do, requires a lot of time, and the most important part, btw).
I have seen many curators vote for authors that turn out to be just stealing identity from a content creator form other platforms... and they are not easy to detect cos they are good at pretending. A good/experienced curator is more likely to detect these shady acts even by just scrolling through an author's blog.