My personal view is NSFW is an image that can be seen from a few feet behind a person's shoulder. If there is strong sexual content, or graphic violence, that can probably be seen from across the room, then YES it would be NSFW. Text on the other can't even be seen by the guy sitting next to you unless they take a peek.
Profanity, while could be offensive, is a different category altogether. Yes it COULD be considered an adult comic is you use it enough, but that's different than NSFW.
My comic makes a pretty liberal use of the English language, and I classify as Saturday Morning Cartoon show for adults (I even have a sign at my convention table that says "Not for children"), but it's not visually vulgar or crass, so I don't label it NSFW.