Honda manual recommend if you are going to warm up ur engine to put it on drive with the ebrake on and it will also warm up just a little faster and if it was bad on any type of way for the engine it wouldnt be in the manual. I read the manual and i dont think honda would recommend anything bad for their cars and i trust the manual. i have a automatic accord so i dont know if you will find this information on a accord not automatic manual.