In this note we deduce a strengthening of the Orlicz-Pettis theorem from the Itô-Nisio theorem. The argument shows that given any series in a Banach space which isn't summable (or more generally unconditionally summable), we can construct a (coarse-grained) subseries with the property that -- under some appropriate notion of "almost all" -- almost all further subseries thereof fail to be weakly summable. Moreover, a strengthening of the Itô-Nisio theorem by Hoffmann-Jorgensen allows us to replace `weakly summable' with `$τ$-weakly summable' for appropriate topologies $τ$ weaker than the weak topology. A treatment of the Itô-Nisio theorem for admissible $τ$ is given.