Hello!
I've posted many NSFW things, both sexual and violent, and I would not consider that right there NSFW at all.
In order to help you determine this for yourself in the future, I will make a list of what is considered NSFW and what needs to be completely censored from what I have understood in communications with staff (after having been reported at one point) and by my own experience.
NSFW:
Genital nudity (Butts are ok, especially since they are often part of a joke. Male and female nipples are treated the same way on Tapas from what I've gathered in previous communications with a staff member on these forums, meaning they do not require a mature content warning unless they are displayed in a sexual light. Nipple vibrators and licking for example.)
Violence involving deep cuts, heavy bleeding, or gore.
Drug use should probably be behind an NSFW warning, however I am unsure on this one since it's not one I have been involved with.
Technically "lewd and strong language" are "supposed" to be behind a mature content filter however this is a rule that is rarely practiced. It most likely only exists to be exercised in VERY extreme cases, so there's a 99% chance you don't have to worry about this one in any writing situation.
Need to be censored even behind a mature content filter (i.e. You can post it, with a mature warning, but the "no-go" parts need to be censored)
Erect penises
Lubricated anuses or vaginas
Ejaculation
Penetration of any kind (mouth, anus, vagina, urethra)
Cannot be posted on Tapas at all:
Hateful content
Content that incites illegal activity (bringing it back to the drug use matter, it wouldn't be fine to post at all if the character or author description told you where to find drugs and a real person to call.)
Content that isn't yours.
Content that links to illegal downloads
Content that links to viruses or harmful sites
Content that motivates people to harm themselves, harm others, do violent acts or commit suicide.
Content that only exists for pornographic purposes.
Child pornography and other content that breaks US law.
In the example you posted, it seems to be presented as a joke and despite being censored, it's not in a heavily sexual or violent context. Thus, I wouldn't say it requires a mature content warning at all.
