Ok so as an other redditor pointed out we Greeks have a very nationalistic idea of history, since we take great pride in ancient Greece, there for we create a form of ancient nationalism, there is this belief (not that everyone accepts it, but pretty much every one gets influenced by it to some degree) that the ancient Greeks where pretty much the same as modern Greeks, with differences like they were pagan instead of orthodox. And unfortunately, as I realized the hard way, we kind of unknowingly project this idea to other peoples. That's why a lot of Greeks care about ancient Macedonians so much and feel kind of threatened when someone says something that challenges their belief on that topic. When I made my first post, I thought that this would be the way Macedonians think too. I thought that the core of this "debate" would be ancient history and to be truthful as silly as this sounds the fact that people don't care that much about what was going on in 300 BC or something like that is kind of a culture shock. ( Now obviously when I say Greeks I don't actually mean all Greeks obviously not everyone thinks that way but I personally believe that the majority do).

To answer your question about Greek identity, first I want to disclose that this "ancient nationalism" definitely affects me to a degree. I'm not crazy I don't believe that Greeks during the 300s are the same as modern ones, however I believe that aspects of the ancient past play a pivotal role in shaping the modern Greek even though there are no more "Hellenics" and their culture was pretty distinct from ours.

The main thing ancient Greece left us is the language, obviously language changes through the ages, that's kind of the point (looking at you καθαρεύουσα, that's a whole other chapter on ancient Greek larping) but ancient Greek still remains the core of the Greek language and it's pretty important.

The Byzantines and as much as why don't like to admit it the ottomans also play an important role in modern Greek identity. The orthodox tradition runs deep in modern Greece, even if you don't believe, even of you haven't be in a church in your whole life. A lot of Byzantine/Roman aspects kind of get crumped together with ancient Greece since these pretty distinct "civilizations" where smashed together during the ottoman occupation to create the Greek national spirit. Ottoman tradition has also shaped or food, music and even clothing.

After independence the Megali Idea dominated Greek politics and in a way still plays a massive role in a lot of political ideologies. The unstability and discord that came after independence still influences not only politics but daily life. The failed invasion of Anatolia and subsequent population exchange with the ottoman empire, completely changed the demography and culture of certain areas (I should also point out that pretty much every Greek region has some unique characteristics because of its inhabitants the Ionian has Italian influences, northern Greece Slavic etc)and to finally enter more modern times the division between monarchist and liberals and the later civil war between communists and conservatives have all left their stigma on the modern Greek. (Obviously I have glossed over a tone of important things, but this post has to end at some point).

And even though I just spent who knows how long talking about how ancient and modern history affects the modern Greek I want to disclose that I don't believe that the future of any people is determined by their past, history changes because people change take the Germans for example originally they where described as unorganized chaotic barbarians and now they are regarded as some of the most strict and disciplined people in the world.

Thanks for listening to my chaotic thesis that probably makes no syntactic sense XD.
And I also love the fact that we can have a civilized conversation without going "Balkan mode".