Actually, this is something really cool and it's only available in this IDE as far as I know. Even though I no longer need this, but it will be helpful for those students using this IDE which often need to print out source as part of the programming assignments. The gutter helps them to write code that will print out nicely on 80-column A4 or letter paper, without having their code wrap unneccessary on printout.
To be less annoying, you should only change is gutter color to grey instead of full black. This is my current configuration.
If I were a lecturer teaching C/C++ classes, I will definitely recommend this IDE.