Were you never curious about what the little [-] did? Where's your sense of adventure! I rib you, but at the same time I understand and your idea has merit.
Not the person you're asking, but I thought the [-] acted as a downvote button and hid the offending content at the same time.
If it isn't, why do some controversial comments get into a lighter font?
You unlock the ability to downvote posts and comments at 500 karma points I believe
Comments yes, posts no. Post downvoting either does not exist or has much higher karma threshold.
You can flag posts, though.
Once you get a certain level of karma you get the ability to downvote comments - lighter font means people downvoted it
I might have used it at some time, but must have forgot it since then. I now find it super useful to be able to collapse long threads, to see what others have posted :D