Comment on “Observation of Fourier transform limited lines in hexagonal boron nitride”

Recently, emission linewidths of single defect centers in layered hexagonal boron nitride down to 50 MHz were reported, close to the lifetime limit. The linewidths were extracted from time traces of laser scanning photoluminescence excitation experiments. At the same time, temporal blinking was affecting the measured time traces even in the absence of a frequency scanning the excitation laser. I argue here that the reported temporal blinking timescale is consistent with the observed transients, implying that the interpretation as spectral shapes and thus the extracted linewidths are invalid.