These pedestrian areas might have been better mapped as area:highway=footway than area=yes + highway=footway (which is arguably tagging for the renderer), but they represent something different to the linear highway=footway ways and should not have been deleted. I have reinstated and re-tagged them in https://www.openstreetmap.org/changeset/148282741

Which lint tool are you using and what was the actual "error" reported?

