I'd first suspect something like the rimbrakes rubbing on the tire, as mentioned in the first thread. This can occur for a variety of reasons, at worst your rims may be out of true (deformation that occurs as the tension in the spokes relaxes with use).

I find it hard to believe that you'd be seeing that much damage from the tire being pinched by the rim, and not be suffering pinch flats non-stop. (Unless you run tubeless)

A proper rim should allow for pretty darn low pressures as long as there's no pinching. It shouldn't be sharp enough to do damage like this with just the deformation of the tire against the ground.

You could also have a faulty tire. The tensile strength of a tire is provided by fibres embedded in it, the severed ends of which are visible in the tear. If something is wrong with them, you'll get tears exactly like this in spots like this, as the rubber alone cannot withstand the air pressure inside it.