Over the years, a variety of ad hoc charge-transfer (CT) diagnostics have been introduced in order to quantify electron-hole in TD-DFT calculations, as reviewed recently. The original purpose of these analysis tools is to alert the user to the presence of a charge-separated state, for which TD-DFT with conventional semilocal and hybrid functionals may fail badly. Remarkably, however, the simple expectation value in eq. ( ) seems not to have been considered as a diagnostic of CT character in TD-DFT calculations until recently, where it was borrowed from careful excited-state analyses in wave function theory. * herbert@chemistry.ohio-state.edu