The relevant text is as follows:
1st Circle – Dance of the Sun and Moon: You embark upon the path of the Careful Sun or the Reckless Moon. Choose one of the following abilities (this choice is permanent):
Reckless Moon: Once per [Encounter], when you make a successful Reflex saving throw against an offensive action that would normally have a lesser effect on a successful save (such as a spell with a save of “Reflex half ”), you may instead ignore the effect entirely.
The 5th circle benefit has a very similar wording, with only two clauses difference.
5th Circle – Cloak of the Sun and Moon: Your devotion to the Careful Sun or Reckless Moon provides additional benefits. Choose one of the following abilities (this choice is permanent):
Reckless Moon: Once per [Encounter], when you make a Reflex saving throw against an offensive action that normally deals half damage on a successful save, you may take no damage from that offensive action instead on a successful save, or take half damage from that offensive action instead on a failed save.
It appears the 5th circle benefit here is simply a lesser form of the first! Do they stack, so that the character can ignore/half one damaging effect and one effect of any type per encounter?
If so, that seems to me like a pretty lackluster 5th circle.
If I'm wildly off base here (for instance, Reflex saves vs e.g. spells might be more important than I realize?), please let me know.