For the uninitiated, generally NSFW is for sexual contents and NSFL is for gory contents. People may want to see one but not see the other at any time for any reason. I have seen this feature requested over the years in Reddit but it never happens. Maybe now some instance can finally implement it?
I don’t care about Reddit (or about growing Lemmy) as much as the average post I see in Lemmy, but if you wanted to migrate people from the former to the latter this is one of the easier ways to help do it. It’s one of those small quality of life things that are asked for periodically. If Lemmy had it it’d be mentioned in Reddit every time people are pissed with the site (which is every day for most sites, including Reddit). It’d be free
mouth to mouthword of mouth (being ESL is funny sometimes) publicity for Lemmy