All traffic over I2P is encrypted unless you use an outproxy (which isn't as common as a Tor exit node is), so no. Most, if not all I2P torrenting traffic never touches an outproxy, just like Tor hidden services (.onion sites and whatnot) never touch an exit node.
Hosting a Tor relay is fine even, as you are still just passing encrypted data around. It's running an exit node that can get you into some sketchy waters with your ISP/law enforcement.
Yeah in some cases, and in other cases it's still just volunteers with really good lawyers.
And even then, there's still no definitive link from the exit node back to the guard (entry) node/relay. And, if you're actually trying to be anonymous from 3 letter agencies, you wouldn't be messing with the clearnet (and therefore exit nodes) through Tor to begin with. You'd probably be sticking to Tor hidden services.