Reconstructed [C II] LFs obtained by combining the abundance-matched L(M) relations with the HMFs of the CDM and WDM cosmologies. The figure uses the LF of our optimistic case and adopts a WDM particle mass of 0.5 keV. While the CDM model reproduces the input LF across all luminosities, the WDM case shows a sharp downturn at the faint end, reflecting the dearth of low-mass haloes and the corresponding minimum luminosity imposed by the abundance-matching procedure.