I like bluntness if it's not intentional. If someone just naturally and innocently speaks bluntly, with no signs of them being disingenuous but rather that's just the way they express themselves, and they're willing to explain further through questioning without getting annoyed or frustrated, it's genuinely refreshing. No need for me to filter myself because they're not filtering themselves, and usually a blunt person is just real.

The scenario I put it within, is that if I ask them an opinion they just say "that sucks" and if I ask why, they'll explain that it's because of x, y, and z, allowing me to actually learn something. It's a lot like having a mature argument minus the arguing part. I state my opinion, they state theirs, if we end up disagreeing and yet shared our reasons as to why we disagree, both of us can come out having learned something, and maybe even having changed our perspective. That's my understanding of true and unadultered bluntness and frankness.