You should consider, from the recipient's "point of view"
what is the prime reference ground. If the "vref" is
developed against ground plane then the recipient ought
to use the same ground plane and any filtering also
returned to it.
When you get to remote or even differently-established
ground domains, it gets real messy.
In IC internal designs I have often "decoupled" bandgap
voltage reference nodes to local signal ground, and made
"images" sent up to the high side and then decoupled
there for high-side-referred voltage reference.
What makes the current loop (of the decoupling cap)
the shortest and least area?
What are the noise aggressor sources and how do they
relate to the input and ground paths, to be snubbed?