The challenge was then accepted by David Brightly at Tilly and Lola. Here is his reply:
And as a Fressellian I accept the challenge. That property is Individual aka Object, the concept at the root of the Porphyrean tree. We can say 'Something exists' with ∃x.Object(x), ie, there is at least one object. Likewise ∀x.Object(x) (which is always true, even when the box is empty) says 'Everything exists' and its negation (which is always false) says 'Some thing is not an object'. But both these last are unenlightening---because always true and always false, respectively, they convey no information, make no distinction, are powerless to change us.
Then Vallicella responds again in yet another post summarizing his objection wonderfully, and then going over Brightly's response, and his counter-response. He demonstrates, to my (untrained, non-Fressellian) satisfaction that "Something identical with itself is a man" does not mean the same thing as "A man exists", and substituting Brightly's "Individual aka Object" for "Something identical with itself" does not seem to solve the problem. However, this is not my field so I'll just conclude by saying I think something exists.
(cross-posted at Quodlibeta)