FWIW, I created a new Public reportsetting for the AP Aging and found it created two new entries in SY_Reportsetting. The printer it pickedup for both was my default printer. One record had a blank field 32 and the other had my workstation name.
Next, I changed the printer on the new setting and saved it. Back in SY_Reportsetting, the printer had changed in the copy that had my workstation name in field 32. On my workstation, I see STANDARD and the custom setting with for my workstation. From another workstation, I see the STANDARD and custom setting, but with the default printer for that workstation. I am assuming it is using the one with the blank field 32.
On a second workstation, I saved a new version of the custom setting and it created a new record in SY_Reportsetting with the workstation name in field 32.
I found that deleting a setting is available if your role has 'Allow Delete Reports for All Modules' in Module Options > Library Master checked. I also found if you delete a setting, it removes all copies, public and private, from SY_Reportsettings.
I inspected our internal system and found that quite a few forms settings have workstation ID now, but in all cases there is a copy with a blank field 32. I could only blank field 32 by agreeing to remove the old key.