I think that ideally, the poster ought to be able to flag their own post for nudity and/or explicit content, or if the poster failed to do so, another user could also flag it, and then each user could choose from three basic options for how content with that flag is handled:

1. The user is fine with that content and it is displayed the same as any other note.

2. The user wants to be able to view it at their discretion, so any images or videos are blurred unless the user actively requests to see them.

3. The user does not want to see such posts at all, so they just don't show up for them.