The breathing marks are clear in the Ancient Library texts (e.g. St John's Gospel), but difficult to make out on Hacker News.

A propos of breathing marks, iota subscripts, and the three different accent marks of Classical Greek, when I learned it at school we had to remember the breathing marks and iota subscripts, and would lose marks if we omitted them, but we didn't need to learn the accents. Modern Greek now has only (acute) accents, which you need to know to stress the correct vowels, exactly where the accents were in the equivalent Classical Greek words.