I started doing this because of my own disability which makes typing far easier, quicker and less error-prone than writing by hand. Most of the Module Managers have accepted it without complaint but when there have been doubting looks, I've asserted myself. I need this because I'm a crip.
I've come to understand that I actually benefit the students by marking electronically. They get more comments, they can read my comments more easily, and if they want to they can ask me for the electronic file. And for any student whose own abiity to type is superior to per ability to write, I hope I'm a role model.