You have valid questions.
First, all engines will have wear, as you know; and certainly there are various types of wear on an engine depending on how it is run, or how it is operated under load.
The recommendations for the higher rpm's on the 998 engine is primarily due to its underwhelming power at lower rpm's.
However, if you have a paddle-shifter, the clutch does not fully lock (engage) until 3200 (+/- 200) rpm's. Running a Spyder in any range where it is not fully-locked causes wear due to the clutch slipping. Over a long period of time, slippage will cause excessive wear on the clutch; if not clutch failure. (An example of clutch failure was provided by a member who refused to run his Spyder as suggested, and he paid the price of having to replace his clutch.)
So you have a couple issues facing you if you have both the 998 and a paddle-shifter.
Now, to further help explain the information provided in the first thread relates to the power-band of the 998 engine (not the 1330). As you know, if an engine is run consistently in a range below or above its power band, the engine is not working at it optimum efficiency -- which translates to increased stress (load) on all of the engines components exposed to this load.
An example would be if you were riding a 10-speed bike up a hill in 10th gear. Your body will be considerably more stressed from the workout from doing so; versus if you were to have used a lower-gear (1st for instance). If you were to have used first gear to climb the same hill, you would have peddled considerably more times (higher revs); however it would have also been considerably easier (less stress) in first gear versus 10th. I believe you get the point. It is similar to an engine.
In addition: the added load on a Spyder's drive-train, when running a 998 engine below its power band, has been noted many times with people having to replace their primary drive bearings and other components. While an engine's speed (rpm) can cause wear and heat, the load factors are an important factor in drive-train failure.
Refer to this info for more detail of a study on aircraft engines:
http://www1.coe.neu.edu/~smuftu/docs...0Espinosa).pdf
When operating any engine below it power band exposes the engine and its drive-train to potential excessive load; which over time can cause failure of components receiving the load.
Lastly, anyone who is a expert rider/driver/pilot will tell you it is best to maintain the vehicle at all times within it optimum range of power and torque for safety and control reasons. More accidents happen when a vehicle is in too low or high of a gear for a specific situation requiring power to avoid it.
You had great questions; and I hope this helped some.
Ride safe...