Unnatural Vitality: When you drop to 0 hit points or fewer and are subjected to the dying condition, you can choose to be dazed, instead of falling unconscious. You make death saving throws as normal, and if you fail one, you fall unconscious instead of being dazed.
Stunning Palm: Until the stance ends, you cannot be dazed or stunned, and you can use the Stunning Palm Attack power.
Stance: A stance lasts until the character assumes another stance or until the character falls unconscious or dies
What would happen to a Revenant Monk currently in the Stunning Palm stance who is reduced to 0 or fewer HP? Are they unable to choose to be dazed? If they choose the option, are they not dazed?