A hard drive is designed for read/write operations. It's no different than copying a file from another drive or network share. He may be talking about continuous operation for extended times. many consumer drives aren't built or rated for 24x7 operation although many of us do run them 24x7. I don't think there is an issue. A server rated drive may last longer under these conditions, but I have run consumer level drives 24x7 for several years without any issues.
As Stated before,... The Hard Drive is Made to Read and Write,... No Problems There! NotEven with Torrents, (as long as they're CLEAN!) ... ~ BUT! ~ It's What might possibly be Within the That Torrent File that your Downloading that just might Cause your Drive and/or Operating System Some Problems or Damage! ~ May the FORCE be With You!
I would just be sure that your system is set up to download torrents to your hdd directly and not the boot ssd, if you use one. There isn't much chance of harming a spinning drive, bit an ssd is really not designed to reach a very old age if the read/write ratio flips from the average users read-heavy workload to nearly entirely writing duty.....
It's actually completely circumstantial. If you have a lot of active torrents seeding/dl-ing 24/7, you will wear the drive out fairly quickly. If you have a few torrents, or a bunch that aren't very active, Windows will power the drive down when it's not in use to save the drive.
It may have something to do with the way the read and writes occur. A torrenting drive is never idling, the heads are moving constantly and that may wear the drive earlier. Still, I wouldn't say "Torrents wear out hard drives". As the other users posted, it's designed to read and write. The wear is negligible.