If a triggered ability does not say the word 'may', is it always mandatory?

Ruling: Triggered abilities without the word "may" are always mandatory and must be put on the chain and resolved when possible.

Nuances:

• The only exception is triggered abilities that incur costs (currently only triggered abilities that target an enemy unit with deflect). You can decline the cost when finalizing the triggered ability, in which case it is retracted and never put on the chain.