Thanks for showing us the beta communities in more details. :)

I've seen you were wondering at some point during the video why your vote doesn't show up, or why you have to refresh to see the post. I believe this is because of hivemind, a fast level 2 layer, but as far as I understand it, when blockchain operations are involved, there will occasionally be a little delay before the hivemind code picks up on the changes (including votes, new posts etc.).

I'd like to give my two cents on a few of your questions. But before I do, I have a question of my own.

*I'm not clear at this point about this aspect: Is joining a community treated as a subscription (so a decision of the would-be subscriber)? Will moderating the community only be done through muting?*

And now regarding some of your questions.

*#2. When a mod mutes a post in a community it's not visible to anyone in that community. Is it possible to mute users for the entire community?*

I may have missed this, can you see the posts from a community if you are not a member? If so, muting a user doesn't seem necessary. If this is possible, you just remove him/her from the community. He/she will continue to see content, but won't be able to post (or shouldn't, considering your last question).

*#3. When a post is downvoted (outside the community) it's still visible within the community. Can only mods mute a post?*

This makes sense to me, partially. I would either leave to the mods to mute a post or to the members of the community. Outsiders of the community shouldn't have any say about the content inside the community, regardless of their SP at the platform level.

If the post is resteemed on a personal blog, yes, then the general rules should apply and the post should be able to be muted by anyone.

*#6 When I mute a post I have to give a reason. Where can I find these reasons?*

I believe this is a sentence or something to tell the member (and possibly the community if it's displayed in the open) why was the post muted. Should be a reason regarding the violation of the rules of the community or common sense or the law, depending how is the community set up and the level of indulgence for various types of abuse mods have.

*#7 Can I make a community where I have to approve members first before they can post in my community?*

I've seen your proof this can happen. YES, I believe the community should be closed for posting, to members only. Maybe with an option to make it open. But then, what would be the difference between a member and a non-member posting?

Anyway, I'm sure details are still being worked on. And feedback like yours will be appreciated.