My guess is that by "the appropriate break point for a line" the author means the break point that makes the result look the best, not just chopping at 13 chara

My guess is that by "the appropriate break point for a line" the author means the break point that makes the result look the best, not just chopping at 13 characters. In order to match what a human would be able to do easily, you'd need to implement something like what tex does (http://en.wikipedia.org/wiki/Word_wrap#Minimum_raggedness http://en.wikipedia.org/wiki/Word_wrap#Minimum_raggedness).