[ietf-dkim] Modified Introduction text for rfc4871-errata

[Barry Leiba]

> Proposed text:
>
>       <t>This currently leaves signers and assessors with the potential for
>         making different interpretations between the two identifiers and may
>         lead to interoperability problems. A signer could intend one to be
>         used for reputation, and have a non-reputation intent in setting the
>         value in the other. However the assessor might choose the wrong value
>         and produce an unintended (and inaccurate) reputation assessment.</t>
>
>       <t>This update resolves that confusion.  It defines additional, semantic
>         labels for the two values, clarifies their nature and specifies their
>         relationship.  More specifically, it clarifies that the identifier
>         intended for reputation lookups (such as white lists) by the
>         assessor is the value of the "d=" tag. However, this does not
>         prohibit message filtering engines from using the "i=" tag, or any
>         other information in the message header, for filtering decisions. </t>
>
>       <t>For signers and assessors that have been using the i= tag for
>         reputation assessment a software change to using the d= tag is intended.
>       </t>

WFM.

Barry, as participant