We point out that the anomalous threshold effect in one dimension occurs when the reflection
probability at zero energy R (0) has some other value than unity, rather than ##IMG##
[http://ej.iop.org/images/0143-0807/38/3/038002/ejpaa68fdieqn1.gif] {$R(0)=0$} or ##IMG##
[http://ej.iop.org/images/0143-0807/38/3/038002/ejpaa68fdieqn2.gif] {$R(0)\ll 1$} as implied by
Ahmed et al in their paper entitled ‘The paradoxical zero reflection at zero energy’ (2017 Eur. J.
Phys. 38 [http://https://doi.org/10.1088/1361-6404/38/2/025401] 025401 ).