POS, and there's no barcode...
A rather large proportion of time in woodworking seems to be spent making decidedly irregular pieces of wood square. At least square in the sense that faces are parallel to one another, and perpendicular to edges. The operations then proceed from this reference form into any manner of angle and curve, but the starting point by necessity is the "4 square" form. The machine responsible for the reference surface and reference edge is the jointer. The planer addresses the surface opposite the reference surface. The table saw commonly addresses the edge opposite the reference edge.
Given the relative importance of the jointer in establishing the first two reference planes, one would surmise that any jointer is designed to achieve both flatness and perpendicularity. As with many things, reality is inconsistent with the theoretical. As a feature, the fence on many jointers are adjustable. Akin to an adjustable sole plate on circular saws and jig saws. There are conceivably instances where cutting or jointing at angles other than 90° is desirable. This would be a great addition in functionality were the primary function of cutting at 90° not compromised in doing so.
At this point, one might guess that this is hardly the case. A fence with an adjustable angle is a fence that cannot be set reliably to 90°. This was true on my Bosch jigsaw, and is acknowledged by Festool with the release of a fixed base on their 2011 line of jigsaws. When the Cadillac of handtool makers cannot design a baseplate for a jigsaw that reliably stays at 90°, it should imply that the Chevrolet's of the industry have no prayer of doing so.
All this to say the fence on my jointer/planer is a piece of junk. It is fully adjustable which means it will not stay at 90°, but I could cut miters, or at least approximate miters. I haven't tried cutting angles, but since it won't stay at 90°, is there real hope of it staying at another arbitrary angle? So a dozen components are required to render the fence, and by extension the machine useless at establishing a 90° edge. There is, thankfully, enough of a structure to devise a fix. It just doesn't seem like a homebrew fix should be required for a $2,000 machine to perform one of its three primary functions.