Wearing 2 Heart Medals does in fact stack the effects. I (obviously) have acquired the 2nd one. Where I used find 1 heart flower growing, I find 2 or 3. A patch of grass that used to yield 1 heart, yields approx. 2 to 3. It really takes the edge off. The one place that they seem to still put the kibosh on the hearts is in small pots in boss battle rooms, they still appeared in the smashed columns in the Koloktos chamber though.
The dialogue is fun in Hero Mode. It helps to pay attention and to choose different dialogue choices, although not quest specific dialogue choices maybe. Such as "Do you want to take this quest?" Those I responded with the appropriate answer. Characters have even noted the fact that I'm attempting Hero Mode in their dialogue, depending on my response.
No matter where you go, there you are.