I flagged a comment by the OP of this question (now deleted) as "rude or offensive".
I don't have access to the comment any more (and don't know if it was eventually removed), but for the <10K+ users it basically was OP's rant about the response the question got (a link to Where to Start?) and how asking a bunch of "computer nerds" was a waste of his/her time and how he/she shouldn't have expected a "socially acceptable response" from the users here. I was moderately surprised when I checked back and found the flag was declined.
Now, I personally don't think that this was overly rude; I just felt it crossed the line of respectable behavior and could be reasonably construed as rude by another user. Now that I think about it, "rude or offensive" could be a bit of a stretch, as this is probably pretty mild compared to some other stuff people have left...
I'm not particularly worried about the declined flag itself; I would just like to know where I went wrong so I can avoid making the same mistake again.
Would flagging as "Not constructive" have been a better choice? Should I be saving "Rude or offensive" for the more vile comments some users might leave?