It's difficult for me to say anything here as I'm rather new, and you have been a member for eight years, but my opinion is that the internet is for everyone, and a public site like this one should be open to all members. If you want a site that is restricted to the people you like, why not open a private site with membership?

I guess that a gallery with restricted entry would cause difficulties for renderosity as it would easliy lead to people not respecting the terms of service of the site, which would cause problems with paypal (marketplace). Besides: if someone comments, it's always their point of view they express. They are free to do so and are responsible for it. If people don't know when they go too far, it's their own time they wasted on that comment, not yours. And you can always inform the mods.

An idea: why not post your work with the comments and rating unchecked, and add a text yourself that friends are asked to write their opinion in a pm?

There are no Borg. All resistance is fertile.