The "I know I'm going to get downvoted for this, but ..." thing is annoyingly common, and unfortunately it's common for a reason: a lot of the time it works: it lets you frame yourself as a victim without ever needing to be victimized.
And, strictly as a matter of fact, it's almost always false. I just did a search for HN comments saying "I know I|this will get|be downvoted" and checked out the first ten I found. Only one of them was net downvoted (which that particular one richly deserved), even though several of them claimed not just to know they would be downvoted but to know that they would be downvoted "into oblivion" or some such phrasing.
So, why do I care? Because (1) these things just add noise and (2) I think that on net they get unfairly upvoted; I want to discourage #1 and compensate for #2. (Also, most of the time comments that say "I know I'll get downvoted..." are in fact bad ones, but that isn't the point here. In this case, the comment itself was pretty reasonable. It just would have been better without the look-how-brave-I-am posturing.)