We refine a construction of Choi, Farah, and Ozawa to build a nonseparable amenable operator algebra
${\rm {\cal A}}$ ⊆ ℓ∞ (M2) whose nonseparable subalgebras, including
${\rm {\cal A}}$, are not isomorphic to a C*-algebra. This is done using a Luzin gap and a uniformly bounded group representation.
Next, we study additional properties of
${\rm {\cal A}}$ and of its separable subalgebras, related to the Kadison Kastler metric.