It was pure c code that was used to print reports, and included the date in a header. Whoever wrote it miscalculated the size of the buffer for the header by one byte. When the date was the longest month & day spelled out plus a two digit day of the month then it would overflow the buffer, resulting in the program crashing.
As far as BitTorrent itself goes, your optimal speed is also going to depend a bit on your client and the number of peers in the swarm.
Suppose you’re seeding a file to 3 peers. It’s not very efficient if your client uploads part 1 of your file to each peer, then uploads part 2 to each peer, etc. A more optimized upload would upload part 1 to peer A, part 2 to peer B, part 3 to peer C, etc. Then the peers can share each of those parts with each other. This way you are effectively only uploading the file one time before other nodes start seeding as well.
The thing is, this sort of seeding only works well in specific situations, including when there’s only one seeder, etc. And not all clients support this. Take a look at qbittorrent’s super seeding option for an example of one client that does.