I need to squeeze an ethernet cable under a door (as I can't drill a wall, Powerline adapters are out of the question, and Wi-Fi has too much of a packet loss to use here), but it doesn't fit whole. If I remove the coating from a small section and pass the four pairs paralel under the door, would it cause any problems? This is an indoor environment without any more electromagnetic noise than the average household, and I have a cat5e avaliable. Thank you.
yes, this may cause issues. The wires inside the insulator (what you are calling coating) is twisted to prevent any interference.
As a network engineer, I have been in situation where everything works fine with a network cable without the insulator. But I would not recommend having it as it may cause degradation in your network bandwidth.