There is a single bit in the trackdisk.device structure to turn off clicking, so it is an os-supported feature and not really a hack. What this bit does is that it tells the device to always step backwards from track 0 to track -1 instead of stepping forwards and backwards (as it does by default).
The clicking is required since it is part of the drive-insertion/detection mechansim, and part of the antique control protocol of the floppy interface.
Now, somewhat more modern drives understand that they cannot step backwards from track 0 to track -1, i.e. if the track-zero detector is active. Thus, they do not click. Instead, they just trigger the drive change.
Some other, older drives, run the step motor nevertheless, but cannot move the drive head. If this is done continuously, then the drive head will decalibrate after a while. Thus, if you continue to hear your drive clicking *despite* using such a program that triggers the trackdisk stepper bit, *remove the program* or it will damage your drive in the long run.
Before you say "that never happened to me" - it did happen to me. I lost one drive exactly of that. Noclick patches help for modern drives, but not for all legacy drives, and it is not enabled by default because it may damage some of them.
