I can only assume that's what happened to me on this question: Is a resistor needed for LEDs in this beatbox project?
We shouldn't downvote because someone answered a duplicate question. I downvote wrong, unclear, misleading, really badly written, and the like.
I have on rare occasions downvoted answers only because they shouldn't have been there. I have only done this a few times, which I think have been when someone directly answered a homework problem.
However, in the particular case you linked to I don't think that's what is going on. You were very sloppy with units. I didn't go into this question before and didn't see your answer before and didn't do any of the downvotes, but I can understand the sentiment. Seeing as you are a established user here, I probably would have left a comment and given you a chance to fix it, but others may have been less charitable or didn't know you have been around here a while.
(12 - Vf)/If = R
(12 - 1.7)/0.020 = 515 Ω
0.02 * 0.02 * 560 = 0.224 Watts
Really!!? You should be ashamed of yourself for that. The more I think about this, I might have downvoted and left a comment and removed the downvote when you fixed it. Neatness, attention to detail, and above all clarity count for a lot. Thinking about it more, if this question hadn't already been closed I'd go downvote your answer right now.