So what is NSFW or Adult?
Not safe for work is very vague. In many workplaces no steemit image is safe. In many others, including steemit itself, adult material can be part of the work. So what is adult? Everyone has their own opinion but we need a clear rule. So we use the same rule used by most social media sites, including Instagram and Facebook: female nipples or genitals mean adult material. Images without them are not tagged as NSFW/Adult. Using the same rule Instagram uses has the advantage of making almost everything here non-adult (the exceptions are posts that escaped Instagram's controls).