Interoperability with Lightning
Assuming the Lightning calendar plugin is used by more than three people on this planet, it might be worth checking out whether its online features (CalDAV, etc) fully respect the Thunderbird proxy settings and thus work with TorBirdy.
A very quick glance with Wireshark under Win7 did not reveal any blatantly obvious direct connection attempts or DNS query leaks, but that doesn't mean anything.
so, in keeping with the other "interop" enhancement requests:
Please state in TorBirdy documentation, if TorBirdy is tested together with Lightning.
Please state if the use of Lightning is recommend, untested, tested, unsupported, supported, discouraged or whatever.
ps: i'm pretty sure Mike knows what hes talking about when he said this would be a rabbit hole you're not gonna get back out of anytime soon ;)