Thanks, @anonimnotoriu! Greatly appreciate it! :)

Appoint them or nominate them and if they gather a certain amount of votes (like for witnesses) from the community members they'll become counselors?

Yes, somewhat like that I have thought of. Still tentative to change but that is the most reasonable way of appointing a counselor. :)

What will be the differences between counselors and the regular members of the community? What does moderation mean in this case?

These counselors can do "sticky" posts on community forums, flag certain post that is not show on community forums (It will still exist in the Steem blockchain but rather just hidden on the platform if flagged), and other features I'm currently brewing. :D