  We present a detailed analysis of the superconductivity-induced
redistribution of optical spectral weight in Bi2Sr2CaCu2O8 near optimal doping.
It confirms the previous conclusion by Molegraaf et al. (Science 66, 2239
(2002)), that the integrated low-frequency spectral weight shows an extra
increase below Tc. Since the region, where the change of the integrated
spectral weight is not compensated, extends well above 2.5 eV, this transfer is
caused by the transfer of spectral weight from interband to intraband region
and only partially by the narrowing of the intraband peak. We show that the
opposite assertion by Boris et al. (Science 304, 708 (2004)) regarding this
compound, is unlikely the consequence of any obvious discrepancies between the
actual experimental data.
