@amiloradovsky Regarding #Mastodon's "visibility".
I plan to implement this in a unified way using #ActivityVocabulary, so the feature could be reused for different social networks. Using the vocabulary, "visibility" means, which groups of users will be able to see the note/activity: Public (all, even unauthenticated), "Users of this instance" etc. or no groups at all and only concrete list of recipients (this is close to "Private" timeline).
Not sure about proper indicators...