". . . on the right . . . on the left" was accepted today (August 15, 2019). According to Natalia302555 and others in this thread, it has been accepted for at least a year. I am wondering why so many entries say otherwise. Is Duo really that erratic? I don't think so.
I see the same on Esta ciudad tiene muchos bancos.. People state one way is accepted but at later dates it is not accepted. I wonder if it is related to platform used. Otherwise, Duo must be that erratic.