I use an inkjet printer, and so I DO tape over the entire label. It has never been a problem.
Can you imagine if your didn't tape over the inkjet printed labels and the label got wet? Your parcel would get lost, no address to ship, OR return to!
The USPS has never complained about me taping over the label.
The only time I can see it being a problem is if you have a printer using heat sensitive paper - the tape adhesive would/could cause it to darken over a short time.