Now that the Magic 2015 FAQ (Release Notes) are published, I hope it is not inappropriate to ask this question.

The Chain Veil
{4}
Legendary Artifact
At the beginning of your end step, if you didn’t activate a loyalty ability of a planeswalker this turn, you lose 2 life.

I find that there are two reasonable ways to read this trigger condition in English that are both reasonable.

#1. No matter how many planeswalkers you control, if you activate at least one loyalty ability for one of them, the condition is not met and The Chain Veil will not trigger.

#2. For each planeswalker you control, if you fail to activate the loyalty ability of any one of them, the condition is met and The Chain Veil will trigger.

The FAQ does not clarify the correct interpretation of this ambiguous English sentence fragment serving as the trigger condition. Which does R&D wish for us to apply?

#1 is the correct interpretation.

Whenever a trigger wants to trigger multiple times for similar-looking events, the templating will be either “for each…” or “whenever…”. Here the trigger condition is “at the beginning of” which can't possibly trigger more than once for that phase or step.

Daniel Kitachewsky
L4, Paris, France
Rules NetRep

It's been pointed out that interpretation #2 is not addressed in my answer.

If #2 was correct, the templating would use “if you didn't activate a loyalty ability of *all* planeswalkers you control”. Here the condition is “if you didn't (activate a loyalty ability of a planeswalker)” where the condition in brackets is true as soon as one has been activated.

Sorry!

Daniel Kitachewsky
L4, Paris, France
Rules NetRep