No argument - it's unprofessional.
Neither have I ever taxied a twin on one - except once after landing with a failed engine.
Edited to add: Runup to leaving employ of HM, on initial IR and having offered CAA IRE control of little twin to fly back, he decides to impress me by cutting both donks as we approach the refuelling pump which has an upslope.
The (almost) inevitable and we stopped short. As he restarted one to complete positioning, I recollect hoping he wasn't so embarrassed that he'd take it out on me at the debrief. He didn't
