Right now, NSFW-marked communities are by default(?) not shown by their home instance to non-logged-in users in the community list, and even if you go to them manually no posts are shown.
Fine, but they also aren't shown to logged in users on other home instances, unless somehow already federated over. If you go to the community's instance, it can't tell you are logged in, and if you go to your home instance you can't see a list of all communities on the other instance that might be available.
Also, older posts that are marked NSFW can't be gotten by anyone with an account anywhere other than the instance they were posted to. When you subscribe to a community on another instance it federates over a few posts, but to doesn't request and federate older posts as you try and page back through the archive. The normal solution is to view the old posts on the source instance, but if the community is marked NSFW the source instance won't let you read the archive there without a local account.
Geeezus ... there i wanted to tell you somehow that the train has left the station. Well then, you being the senior admin of a specialised instance, and me being a newcomer who purposefully has an account on a general-purpose server roughly in my area, perhaps we can agree on the fact that the system seems designed to both handle special-purpose sites (which is a kind of centralisation) and general-purpose aggregators (which in effect acts as a centralisation at different aspect)? ... I will not argue with you but you will also not command others. And btw. why is there no federated user-namespace if it is so that servers are thought to be of themed purpose?
Have a nice day/evening. ;-)