To cut or not to cut

I've been asked this question before, so why not let you answer it. When using plasticell foundation in brood frames, do you trim the corners, along the perforated line, do you cut an even larger part of the corner off, or do you just leave it the heck alone. I've been told that you need to cut it because bees don't like walking on the wood. What's your opinion or practice? And why?