Extended descriptions print on forms.  If the comments are internal, a UDF to store your extra text might be worth considering.

I don't mind the ext descriptions/comments printing on forms - just interested in what would be the easiest to implement. Thank you for the help.

Easiest depends on the details.

Something that follows a product line would be easiest with a UDF in that table (instead of maintaining the extra text in all items).

Something that is the same for many items might be easier to import into a UDF.

Descriptions that change item by item always, but rarely in the transaction, would be a good fit for extended descriptions.

Repeated text that is chosen for the transaction might be easiest with custom comment codes (eg. /TERMS1...).

Etc...