Is it normal for incision sites to leak puss after surgery?

Pus is not considered normal after surgery, and might indicate an infection.  It should be checked within 24 hours by your surgeon and/or their associates.

Congratulations on having undergone the breast reduction procedure.  Although some drainage from incision lines is not unusual after breast reduction procedures, the drainage of “puss” is not normal. Puss, by definition implies an  infectious process. Whether or not you are really draining puss versus serum, is best evaluated by your plastic surgeon, who will always be your best resource. I would suggest that you request follow-up (earlier than already scheduled if necessary) for in-person evaluation. Best wishes; hopefully, you will be very pleased with the longer-term outcome of the procedure performed.

Are you sure it is puss?  Or is it some separation of the incision?  Best to be seen by your surgeon in person to be properly evaluated.