All three of these can be used around unnecessary information. So what’s the difference between the use of each?

• They can all be used to identify material that acts as an aside, such as this brief comment, or to add incidental information.
• They can all be used to identify material that acts as an aside (such as this brief comment) or to add incidental information.
• They can all be used to identify material that acts as an aside—such as this brief comment—or to add incidental information.