  We calculate the quark self-energy at one-loop level at high temperature,
taking into account contributions from both the (chromo)electric scale $gT$ and
the (chromo)magnetic scale $g^2T$. While reproducing standard massive
excitations due to the electric scale, we uncover a novel massless excitation
ascribable to the magnetic scale. The residue of this massless excitation is
nonpositive at all temperatures, which consequently gives rise to positivity
violation in the quark spectral functions. This demonstrates the profound
impact of confinement effects on thermal quark collective excitations, which
manifest genuine long-range correlations in the system.
