From the perspective of D-brane physics, we consider the role of the
real intrinsic Riemannian geometry and describe the statistical nature
of gauge and exotic instanton vacuum fluctuations. For the
Veneziano-Yankielowiz/ Affleck-Dine-Seiberg and non-perturbative
instanton superpotentials, the issue of the wall (in)stabilities is
analysed for marginal and threshold like vacua, and their arbitrary
linear combinations. Physically, for both the stationary and
non-stationary statistical configurations with and without the
statistical fluctuations of the gauge and exotic instanton curves, the
Gaussian fluctuations over equilibrium (non)-stationary vacua accomplish
a well-defined, non-degenerate, curved and regular intrinsic Riemannian
manifolds for statistically admissible domains of (i) one loop
renormalized mass and vacuum expectation value of the chiral field for
the stationary vacua and (ii) the corresponding contributions of the
instanton curves for the non-stationary vacua. As a function of the
vacuum expectation value of the chiral field, the global ensemble
stability and phase transition criteria algebraically reduce to the
invariance of the quadratic and quartic polynomials.