This blog post from a few years ago suggests that using BitTorrent services over Tor is a bad idea for multiple reasons. However, it also suggests some fixes to get over these problems.
Is using a
It doesn't make you anonymous. Torrent protocol wasn't designed with anonymity in mind and there are a million ways you're going to leak your actual IP address.
Tor is a TCP only network.
While this doesn't give you the anonymity you wanted, it will hurt the network for other users.
I pay monthly for access to a SOCKS5 proxy service from a company called BTGuard, and tell my BT client to connect through that. It is not expensive and works great I've been using it for about 12 or 13 years, and found it after getting an email from my ISP saying they identified me downloading TV shows. In that time, I have only had issues a handful of times. More reliable than most other services I pay for and I've never seen another DMCA notice since.
I didn't think people torrented over TOR. Aside from the security issues (which I didn't know about in the first place), I would think it's gotta be insanely slow. Is it not?
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.