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Detecting exit nodes is error prone, as you point out. Some exit nodes have their traffic exit a different address than their listening port. Hey does Exonerator handle these?

Right. It's not trivial for tor to figure out what exit relays are multi-homed -- at least not without actually establishing circuits and fetching content over each exit relay.

I just finished an exitmap scan and found 17 exit relays that exit from an IP address that is different from what's listed in the consensus:

This mode of operation, regardless of how it happens, is not in itself a problem, nor cause for alarm. In fact, the nature of these "exit IP different than ORPort" relays can and often does assist users in circumventing censorship... a fundamental use case of Tor. For instance, the arbitrary automated and blind blocking via dumb blocklists that prevent even such most basic user activity and human right to knowledge as simply reading websites via Tor. Such blocking examples can often be found here: https://trac.torproject.org/projects/tor/wiki/org/doc/ListOfServicesBlocking... It's also entirely up to the exit operator to determine if the third party non contractual / SLA exonerator service is of any particular use or benefit to them or not... perhaps they have other notary means, or are immune or not subject to any such legal or jurisdictional issues, for which it becomes moot. Similarly, realtime TorDNSEL and the like could be considered to be censorship enabling tools.