  In recent publications, Borra (2013); Borra & Trottier (2016); Borra (2017)
claimed the discovery of ultra-short ($10^{-12}\,$s) optical pulses originating
from stars and galaxies, asserted to be sent by extraterrestrial intelligence.
I show that these signals are not astrophysical or instrumental in nature, but
originate from the non-random spacings of spectral absorption lines. They can
be shown to arise in their clearest form in synthetic solar spectra, as these
do not suffer from noise.
