@mtdowling: I only beg to differ, that's all. If your ValuesInterface offers multiple values for the same name - and you hint Field with it - *then* it is the wrong name because it breaks the "field-name : field-value" pair that is distinct in HTTP nomenclatura: one name, one value in HTTP "field-name : field-value" pairs. Pointing to the grammar is also somewhat off-side as in RFC 2616 this an ABNF for tokenization and syntax, the meaning is within the text, not within the grammar. If you remind that this is not an AST, it's also not a lexer nor a tokenizer. However an Interface is a contract and therefore must provide a fitting model independent to the underlying implementations. That's normally best done with a reduced interface and not so much painting, features and flowers. I somewhat become more and more certain, that there is implementation context leaking into this specs. With the needed respect, I honestly motivate you to more critically get on that point. I think there is a relative high risk the this suggestion does much more than just specifying some interface to interact with HTTP messages. Perhaps write some tests that verfiy that all features are actually needed for interacting with HTTP messages? __toString(), return self, factories - all these already are filtered out by such requirement tests. Don't get this wrong, I would also honor these, even if not part of the standard. But you should understand as you wrote this spec why you actually introduced them and ask yourself if those really belong into specs.

In another comment today you also wrote:

> With regards to this proposal, `__toString` is not going to be removed from `HeaderValuesInterface`. 

You do not say further why, you just state that. I find this pretty poisonous for a critical review of the proposal because this sounds like it's forbidding to think about certain changes. All I can see is that you're somewhat in love with the `HeaderValuesInterface` which certainly has it's place, but a critical review should show such place more clearly, so there is nothing IMHO that needs to be defended that way. That comment more on the meta level, but I'm really missing here your sharing your motivation for such places next to saying that you have not planned to change these. Otherwise I can not follow it.