Coptic (for those who do not know) is the ancient Egyptian language written in Greek characters. The earliest dated Coptic inscription dates to 200 B.C. It mostly died out by the ninth century but there was a revival and late flourishing in the thirteenth century A.D.
Those who read Coptic manuscripts (and Coptic is not the only language whose manuscripts have this characteristic) know that Coptic manuscripts do not put spaces between words. Published versions of Coptic manuscripts put spaces between the words, but those spaces are not usually found in the manuscript. So a non-trivial problem is how do we know that a space should go between letters. Different editors solve this problem differently. How would we know where an ancient Coptic speaker would divide the text into different word units? The ancient Coptic scribes actually left some clues but these clues are often either ignored or reinterpreted (and sometimes misinterpreted) by modern editors.
This is just one of the many problems that confronts an editor the minute he or she undertakes to edit a text. Modern writers tend to give it no thought whatsoever. For us, the problem has already been solved.