In many GP transactional screens you can input a comment. The comment functionality was intended to be used for repeating comments (things like "Remember to send your invoice to our new address", "Thanks for your business", etc.). Consequently comments have a comment ID to reduce keying and allow for consistent verbiage. It's easier to key or default "Thank1" than "Thanks for your business".
Since comments print on most default documents, their use often evolves into one time customer comment use, in place of consistent repeating comments. Things like ("Red gromets shipped in place of black gromets"). However, if you create a comment ID for each comment ever made on an invoice, order or P.O. you're soon drowning in comment id's.
Well in case you missed this functionality, you can skip the comment ID altogether. Simply click the blue arrow next to a blank comment id. Create a comment without ever entering an ID and you've got a nice way to provide one-time communication to your customers or vendors. These comments print just fine on orders, invoices, P.O.'s, etc.
This also allows easy separation of external facing notes (the comment) and internal facing notes (the note field). Also, since comments are already sent to print on default documents you don't have a bunch of modifications to do. No linking tables to add the notes field to a report.
So there you have it, "Thank you and have a nice day!".