This page aims to collect common pitfalls and trivia, which may be useful in debugging more the esoteric issues that can arise.
Nylon is Asynchronous
Nylon processes nodes asynchronously from Godots process/physics process. This means messages should be treated like InputEvents, as they can be emitted at any point during a frame. Furthermore, new messages will continue to be emitted even while you may be awaiting or executing deferred calls in response to a message.
As an example, if you were to await in a function triggered by message A, message B will still be emitted and may trigger a new function call before message A has been processed. You may wish to queue messages if this becomes an issue for you.