We recently upgraded from 3.14.x to 3.16.3 and the staff feels that the fix in bug 10310 to "prevent submit form pressing enter" is a regression. Previously they were able to submit a new item by just scanning a barcode (where the scanner submits [enter] after the barcode), but with 10310 that is no longer possible and since they prefer using the keyboard it's either a lot of tabbing or getting a hold of the mouse to click submit. The dummy submit button that prevents implicit posting of the form by hitting [enter] is necessary for the current layout of additem.pl. My suggestion is to split additem.pl into three tabs "Add item", "Add & duplicate" and "Add multiple items". That way implicit posting could be allowed and our librarians be happy again when adding new books.
Given the age of this bug (reported against 3.14) I believe that regression noted here has moved into 'new standard behaviour'. More so I believe that submitting forms on reading barcodes outside of circulation actions would not be a good idea or at least quite controversial. Marking WONTFIX, please reopen if you disagree.