Originally Posted by Fraz
It's not for you - that's why. It's for the person marking it to be able to easily write comments/corrections

Not on a dissertation, they are not allowed to write or make corrections on the document, any comments are written on a seperate form and returned to you along with one copy of the dissertation. I do see your point when it comes to marking other essays. But mostly, from what i can gather, it is to help the lecturer to read what is written, i.e. easier to read when it is spaced out rather than clsoe together, especially when they have to read 100s of the things.