Edit: I misread the statement. Thanks for pointing this out to all the repliers! My fault.
The first point of the answer is misleading. Tor is indeed designed with anonymity in mind. The leaks occur in different layers, like the for e.g. chosen BitTorrent client.
https://blog.torproject.org/bittorrent-over-tor-isnt-good-idea/
If you have trouble because the clients do not support native oauth, you can try to use a auth dameon like https://github.com/ltratt/pizauth