The main question of the quote is: if we introduce a system that rejects a "large" amount of Elixir code, will developers adopt it? If some language features are only available for "untyped" code, will developers often forego types only to get those features? And if that happens, could we end-up "forking" the Elixir community, where part of the community uses some idioms and the other part uses others (which is a common complaint about large languages)?
The goal is not to reject types but rather to find a theory that mirrors the language as close as possible. I believe balancing these trade-offs will be essential to the adoption and success of a type system in Elixir.
I use Elixir whenever I can, and I would love a better type system (though I admittedly suck at using what Dialyzer already provides, which is extensive). I'm very excited to see where the current effort goes!
But absolutely, if new types break existing Elixir code and idioms it would result in a schism that would be devastating and disastrous to the Elixir community. I for one am really glad you are asking these questions, and FWIW I think you're doing exactly the right thing.
The goal is not to reject types but rather to find a theory that mirrors the language as close as possible. I believe balancing these trade-offs will be essential to the adoption and success of a type system in Elixir.