Basic idea:
  Set up another email list which basically is just a filter applied
  to d-d-l posts.  Make sure to announce it widely so that those who
  don't want the full d-d-l level of spam can still stay informed.
  The basic mindset should be that if any doubt at all can possibly be
  found about the general usefulness of a given message, no matter how
  small and who it is from, don't let the email flood everyone's
  inbox.

Special rules:
  - Email posts accepted for posting at d-d-l are automatically sent
    to the moderation queue of the new mailing list [1]
  - No direct posts to the list are allowed (in other words,
    subscribers to this list should be treated as subscribers to d-d-l
    as far as d-d-l moderation goes) [2]
  - Moderators may decide that a special summary email should be used
    instead of letting individual emails through [3]

Extra abilities that would be nice:
  - The ability to require multiple approvals to allow an email to be
    posted [4]
  - Some mechanism for having core hackers say, "You may want to
    reconsider whether to accept this one email because <reason>" [5]
  - It'd be nice to prepend messages with extra information--or even
    truncate the email (with sufficient notice that such has happened)
    [6]
  - It'd be nice to have a way for a subscriber to look at a special
    summary email (see Special rules above) with links to individual
    emails and request full messages to be delivered to their inbox
    [7]

Incomplete list of reasons why a post would be offtopic include:
  - "pie in the sky" ideas
  - proposals made by those who are unwilling (or unable) to do the
    majority of the work to implement those proposals
  - any emails that result in "bike-shed effect" follow-ups [8]
  - any emails or threads that are excessively long, despite otherwise
    being very on topic (and perhaps even if it's an item that sorely
    needs to be discussed) [9]
  - request for comments on a case-by-case basis [10]
  - anything that is not relevant to _at least_ two or three products
  - freeze break requests (partially due to the rule above, but I'm
    mentioning it as a special case; if people really want to see
    those, they should subscribe to d-d-l or r-t)
  - anything for which there is a better email list (e.g. gnome-list,
    gnome-announce-list, usability, etc.)
  - anything that doesn't match the moderators' capricious whim  ;-)

Extra notes:
  - d-d-l should still be monitored for off-topic posts as has been
    done traditionally (i.e. lax but with limits), both because it
    should still be useful for those who want and can keep up with a
    broader amount of community feedback, and because it will reduce
    the work of moderators handling the new mailing list.  Besides,
    with no moderation d-d-l will die completely and will result in
    the death of both mailing lists.

Rationale:
  [1] We don't want to have to moderate spam from non-list-subscribers
      twice (once in d-d-l and once in the new list)
  [2] One of the big problems about d-d-l is the fight of
      too-exclusive versus too-noisy.  By having all posts go through
      d-d-l everyone is allowed to see what's going on, but core
      hackers that don't have the time for reading d-d-l can instead
      read a filtered version.
  [3] A commonly reported problem from people who remain on d-d-l but
      try to manually filter it by only reading select posts is that
      mostly useless threads will frequently contain at least one or
      two useful nuggets of information.
  [4] There's an awful lot of rules for filtering stuff.  Moderators
      may feel too much pressure and reject too many messages if they
      feel it is up to them to reject all useless messages.  Besides,
      this seems to work well with the release team (even if that's
      much more important)...
  [5] This list is designed to provide a lot of pressure to reject
      messages.  That's healthy.  But it's possible that a mistake
      could be made or that subsequent emails or information would
      make a previously rejected message more useful.
  [6] In case an email is considered useful but happens to reference
      previous less-useful ones, it may be helpful to provide context.
      Similiarly, it's possible for an email to consist of multiple
      topics only one of which is more widely useful
  [7] This would make it easier for people to respond to threads while
      not breaking the threading mechanisms of email clients for those
      following d-d-l.
  [8] Note that these can be handled by the thread summary special
      rule in order to handle useful portions
  [9] This may seem somewhat controversial, because there are a number
      of really awesome definitely on-topic and sorely needed threads
      that match this description.  However, rarely is it the case
      that everyone needs or wants to read all the information; it is
      quite likely that occasional summaries with links to all the
      relevant emails on d-d-l will suffice.
 [10] Many requests for comments (e.g. themes) would be better handled
      by one (or more) thread summary emails.