Sling load,
The tail rotor is made purposefully quite simply, and more robust because the weight trade-off against the cost of the extra components makes simplicity a virtue. The typical tail rotor has no lead-lag and no cyclic so it is stronger relative to its thrust than a main rotor. One means of relieving the flapping forces due to forward flight (disymetry of lift) is to incorporate lots of delta-3 coupling (pitch-flap coupling). Note that the blade flapping (or teetering) axis induces considerable washout of the collective pitch. This is done by making the flap occur at a different place than the pitch change horn. As the blade flaps, the pitch horn doesn't move, so the collective pitch is changed. In a hover, little flapping occurs, so this feature does not reduce thrust. In forward flight, the forward sweeping blade builds more lift, flaps away from the vertical tail, and so gets its lift reduced. This balances out the forces, and relieves most of the bending that the shaft and gearbox would otherwise see.
The blade is symetrical, mostly for simplicity, and it has little twist because of the simplicity. Also, it must work to thrust in both directions, and the twist would hurt the right pedal thrust.
The fenestron has many blades packaged tightly, and would be a problem to allow flapping. Also, the fenestron needs tight tip clearance for high efficiency (almost touching the shroud). This would be a problem if significant flapping were allowed. The shorter blades are more easily stiffened against bending, as well. But the biggest reason why the fenestron blades need no flapping relief is that the duct shields the fan from the disymetry forces, so the disk gets almost no differential bending due to forward flight. The fan behaves as if it is in a regular hover, even at high speed. That is one of the reasons why Comanche has a fan, and why it can do the "snap turn" at such high speeds. The fan sees almost no bending, and so does things that would very highly stress a tail rotor (such as the big sideslips of the snap turn.)
The fan's blades are highly assymetrical and twisted, for very careful efficient design in hover, where thrust is most important, and where the small disk of the fan would otherwise cost lots of power. The opposite thrust (right thrust for American designs) is not as efficiently developed as a result, but this is only needed at autorotative descents, where a bit of extra power penalty is hardly noticed.
