As explained in another blog post, dialog comments can not be retrieved and used from the process without writing a plugin. If you just want to see what people are adding to the comments area, you can use advanced find. The comments are stored in the process sessions for the dialog.
When you open a specific process session, you can scroll down to the comments section and see what the user entered.
You can also set up a simple advanced find to see your comments and export them to a spreadsheet.