What does "civil" mean?
"Civil" does not mean necessarily mean "supportive", or even "friendly". Comments, especially on challenging topics, need room for disagreement and debate; even passionate debate. We don't all have to agree, but we must be able to disagree without personal insults, harassment, and abuse.
When reviewing other people's comments, you're asked two questions: is it "good", and is it "civil". You're likely to come across comments that you think are stupid and/or make you angry. You should rate these comments as "not good". However, if the comment isn't a personal attack, harassment, or abuse, you should still rate it as "civil". Comments can easily be both "bad" and "civil". The reverse is also true: you may find comments you like/enjoy/laugh at that are also attacks/harassment/etc. You should rate those comments as "good" and "not civil".
It's entirely possible to disagree without resorting to personal insults and attacks, and it makes for a much more interesting debate.