This is an continuation of my last post, specifically a comment from @rufus@discuss.tchncs.de:
It will never get recommended. It’s bad for the network and bad for your privacy.
Excluding that doing so is bad for the network, why it is “private” using VPN but not Tor, inferring from common consensus. The main point in the blog post is a protocol level problem:
apparently in some cases uTorrent, BitSpirit, and libTorrent simply write your IP address directly into the information they send to the tracker and/or to other peers
Tor and VPN are both transports what wrap other traffic within. If that statement is true, no transport can save the information leaking nature of the BT protocol itself.
It’s probably more they either optimize for speed or for privacy. You sometimes can’t do both. Including IPs is usually done to find the best and direct connection between peers. It’s not shady per se. But it’ll harm you if it’s the default.