Wasn't RDFa created exactly for cases like this, so you could attach any kind of meaning to any block/element in your document? The NSFW tag (and MildlyNSFW and

Wasn't RDFa created exactly for cases like this, so you could attach any kind of meaning to any block/element in your document? The NSFW tag (and MildlyNSFW and SFW and SARCASM and...) could then be something that's supported by, say, input fields for comments, but converted to RDFa when submitted.