It's easy to blur the posts that are tagged with NSFW but the community icon that goes with a lot of those posts are also NSFW. Not sure if Lemmy provides a way to know that about the community or if there's some other way blurring or hiding those icons could be achieved.
See screenshot for an example.
I wonder if it would be easier to just disable avatars for NSFW communities. Just have a little 18 plus icon or something.