- What happens when a node creation request is accompanied by a configure
  node, but node configuration is not implemented?

  Solution:

  Reply with a not-acceptable stanza error, with a node-not-configurable
  error attached.

- Node purging with many items in storage and notification of retraction enabled
could produce a large number of notifications. Suggestion: instead send a
<event><purge/></event>

- Examples 58 and 62 are the same

- What error to return for outcast user requests?
  - What if some admin requested it?

- Why not return forbidden when JIDs do not match on subscription?

- What to do when receiving an unsubscription request with a subid, when
  subids are not supported? Ignore or reply with bad-request?

- unsubscription: why check for the requestor being subscribed. You want to
  check if the jid is subscribed. An not-authorized can be sent if the
  requestor and jid don't match. Otherwise, unexpected-request might
  be appropriate when the jid is not subscribed along with a special
  child element of not-subscribed in the pubsub#error namespace. 

- 8.1.7 states:
    If subscription identifiers are supported by the service and the entity's
    subscription is not NONE or OUTCAST, the 'subid' attribute MUST be present
    as well as the 'jid' attribute.
  There is no such thing as a subscription of 'OUTCAST'. Also, I'm not sure
  why NONE is capitalized.