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Most torrent clients I know of write to disk far too often
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In my experience when appending or overwriting files, FAT32 tends to favour in-order allocation of clusters. Also, if it doesn't have to move something... why move it?
Indeed, the bane of SD cards is log files, which might be written to the same spot over and over, so long as the size doesn't change dramatically.
I don't have any knowledge about vfat or how Linux handles all this, but I know FAT32 on Windows isn't doing any of that wear levelling you say it should.
The first part of the SD card will probably wear out long before the last parts, which means your card is either going to drop in capacity or be rendered useless well before it should.