  Recently, Sironi (PRL, 128, 145102; S22) reported the correlation between
particles accelerated into high energy and their crossings of regions with
electric field larger than magnetic field (E>B regions) in kinetic simulations
of relativistic magnetic reconnection. They claim that electric fields in E>B
regions (for a vanishing guide field) dominate in accelerating particles to the
injection energy. S22 presented test-particle simulations showing that if
particle energies are reset to low energies in E>B regions, efficient injection
is suppressed. This Comment re-examines these claims by analyzing a simulation
resembling the reference case in S22. We show that during crossings E>B
acceleration only contributes a small fraction to the injection energy as E>B
regions only host particles for a short duration. The energization before any
E>B crossings has a comparable contribution, indicating E>B regions are not
unique in pre-accelerating particles. A new test-particle simulation shows that
zero-outing electric fields in E>B regions does not strongly influence the
injection. We suggest that the procedure used in S22 to exclude E>B
acceleration partly removes acceleration outside E>B regions, leading to a
false conclusion.
