I feel like I've suggested this before, but I couldn't find it in a quick search, so I thought I'd create a thread for it just in case.
When a doctor heals someone, any attacks on that person should produce an immunity message.
Getting outed as immune is one of the main causes of death for evils. This change only helps a little bit (realistically, if it's actually outed publicly and you claim to have been healed, towns will ask the Doctor to reveal, and honestly most smart evils will claim, via DN, that you were immune even today, regardless of how you actually survived), but it will still help. Generally, having people aware of your immunity is such a devastating problem for NKs right now that they could use all the help with it they can get. Even if you're still likely to get outed and killed, adding more uncertainty to the Mafia's knowledge of your role is valuable.