How do you enter them nowadays by the way? In the early days of the internet before unicode there were special fonts from SIL for example that first of all were using Latin characters (you'd type W and it would look like Ω) and secondly I think had the diacritics as separate characters, so the font would combine them. It was messy but at least you could type it on a normal keyboard. You could even read it in its ASCII form, most of the hacks were pretty reasonable.
Personally I type Greek using a vim keymap file, usually when writing LaTeX. I believe my keymap file is influenced by those older non-Unicode fonts, because I type w for ω and ;h for ή and >~h| for ᾖ. But my fellow students would mostly use Word. I don't know how they would type the letters, but commonly they would mix the tonos letters with everything else. I think what was happening is that Word would automatically substitute fonts that offered those codepoints, so it would end up showing Times for the letters with tonos and Palatino for the others (or something like that). Hence the ransom note effect.
Here are the two Unicode ranges (PDF):
modern Greek: http://unicode.org/charts/PDF/U0370.pdf
ancient Greek: http://unicode.org/charts/PDF/U1F00.pdf
Then again, try explaining to tech people the difference between ή and ἠ and how you can get ἤ or ᾔ. :-)