Comments
We've had a few clients also comment about the same thing - the red asterisk on the PO is confusing for the user raising the PO. The above is a workable solution, or even if it was something on the Purchases & Payables Setup that would allow you to choose whether you want the field marked as mandatory/required.Most of our clients don't generate invoices from PO's, they only receipt the PO lines and then have solutions like Continia Document Capture to process their invoices, where they match to receipt lines.
Ideally this should be combined with a possibility to tag those attributes that are important for production or procurement, because there should not be ALL attributes shown there. Look at my LInkedIn Post "Using engineering attributes for specification management "! if you want to get more context on that.