Much to my suprise the output of the "name" operator does not give an Item when piped into the "itembyname" operator.

What is the expected format for the name of the item in "itembyname"?

The name operator returns the localized name of an item, as shown to the player ingame. The itembyname operator expects the unique identifier of an item, like minecraft:stone and minecraft: pumpkin_seeds.

Could you put that information into the tooltip description of "itembyname"?

Sure.

I wonder if it's also worth making an operator that gives the registry name of an item.

@josephcsible Good point, will incorporate that in this issue.