When evaluating lens performance, one-offs are a Bad Idea, as is any single test, particularly any single test on a planar target at one distance; it’s important to evaluate a lens at various distances and on “3D” scenes, not simply planar targets. This is why I like to couple field shots with more controlled comparisons.
Hence this followup confirms the lens skew behavior on another scene, providing both confirmation and perspective, and an analysis on the significance of the effect in terms of how far to stop down. Apertures f/1.4 - f/8 are shown along with large crops.
Combined with the other examples a fairly complete picture is now in place in my review of the Sigma 35/1.4 DG HSM.
This discussion really applies to any brand lens on any camera. I have observed such issues with Nikon, Canon, Zeiss, Leica M, Leica S, Olympus, Sigma— no brand exceptions. See also Brand New Blur.