Yes, if done with a blip of the throttle to reduce the load, or at a sufficiently low RPM.
Are you saying clutchless downshifting is OK?
The typical motorcycle trans is designed to be a non synchronized unit, and to change from one speed to another without the benefit of the gear speeds being matched up. They are designed to endure this up to a certain practical level, and the use or non-use of the clutch matters only insofar as it bears on the amount of load placed on the transmission during the gear change. Dragging the two currently engaged gears apart under a heavy load will tend to round over the locking lugs, as will having the lugs of the gear being changed into come into contact with each other before they completely mesh, or under an excessive impact.
Exactly where the point of the load being excessive is is somewhat nebulous and hard to define, but I shift with no clutch quite often under a variety of conditions, and I have historically had less transmission trouble than almost anyone I know.
A clean, quick shift under a reduced load is the healthiest thing for the gearbox, regardless of whether the clutch is used or not.
Another unsupported gratuitous assertion. You have no idea when or how that fork was bent. The fact is that such things normally occur over time rather than due to a single incident.
Come to englnad and i will show you a bike that bent the selector thats used for changing from 4th to 5th gear. This happened while on the back wheel. Our local yamaha specialist has repaired a number of bikes with this exact problem and says its caused by clutchless changes from 4th - 5th.