It might be. But it really depends on how it's done. Professional restorers have specific techniques to clean without causing harm. For amateurs, it could be risky and might not be considered true restoration if it causes any negative effects.
It's not that hard. First, you need to have a good grasp of basic drawing techniques. Then, start with simple sketches and gradually build up the details. Pay attention to shading and line quality.
You could draw a magic trick scene where a magician waves a wand and the pencil vanishes. Or maybe have a character put the pencil in a box and when the box is opened, it's gone!
Well, one option could be to use a gentle solvent or cleaner. But be careful not to damage the comic. Test it on a small, inconspicuous area first. Another approach is to lightly scrape the grease pencil mark with a fine sandpaper or a very sharp knife, but this needs to be done with extreme caution to avoid causing more harm.
The art style can vary greatly. Some may have a highly detailed and realistic style, while others might be more simplistic and cartoonish. This allows for a wide range of expression and storytelling. For instance, Calvin and Hobbes has a simple yet very expressive style that helps bring the humorous adventures of the boy and his tiger friend to life.