Is it a special key in some keyboards?
<font color="blue">[i]If there is no struggle, there is no progress!
You need to define precisely what you are trying to do. Are you using Vugen? If so, commenting lines is easy. Did you search Vugen help?
"How to perform CTRL+ OemQuestion on the keyboard to insert comment to existing lines?" // I'm not sure I get what you're writing about here.
Is it a special key in some keyboards? /* or here */