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?
That's a good idea. The client could let the user select their phobia from this list of all phobias from Wikipedia with a description and then filter for the tags matching the description.