The new Ixalan card "River Heralds' Boon" says:
Put a +1/+1 counter on target creature and a +1/+1 counter on up to one target Merfolk.
The subtype "Merfolk" can apply to non-creatures, including Merrow Commerce and Aquitect's Will. My reading of Comp Rules 114.2 is that an Aquitect's Will on the stack is not a legal target for the Boon, but what about Merrow Commerce? (Yes, I know it will normally be useless to put a +1/+1 counter on an enchantment. Maybe you're planning to cast Opalescence later on. Whatever.)
Could you target a creature and a Merrow Commerce, and put counters on each of them?