This is a different kind of question than is normally asked, but since Ancient Greek is on-topic for the meantime, I think this is a surprisingly good place to ask. I wanted to get the opinion of those who might know. Does learning Modern Greek help your knowledge of Ancient Greek? I can think of at least a few reasons why it may.
First, there is a shared vocabulary, and anything that makes you more fluent in that shared vocabulary is a good thing.
Second, I find that knowing English improves my knowledge of Latin, because it gives me a greater appreciation of Latin, seeing Latin roots and constructs show up in my own language. This is somewhat psychological—if you appreciate a language more, then you will have more motivation to learn it, and thus acquire a better knowledge—but I think most people can testify that it's true. By analogy, the same could be said of Greek.
Do you think it's reasonable to expect that learning Modern Greek would help me feel more comfortable or become more knowledgeable in Ancient Greek?
I'm interested in both first- and second-hand experiences of learning the two languages, as well as the opinions of those who know one and not the other.