I think there's some nuance here. Being liberal in what you accept is good for the growth and connectedness of a network. It's so powerful that it's not so much

I think there's some nuance here. Being liberal in what you accept is good for the growth and connectedness of a network. It's so powerful that it's not so much a suggestion as an inevitability -- if you're trying to be perfectly strict, then you will be excluded from the network and other people will find a way to be included. A party will always be bigger when you are less strict about the invitation/rsvp protocol. But it has obvious downsides. One is that the protocol keeps evolving, because people find novel ways to be non-conforming senders. This means an implementation is never "done". Another is that it becomes so hard to create a new implementation that accounts for all the non-conforming behavior, that the "standard" essentially becomes defined by a few of the big implementations.