Users not subscribed to digest unless they submit digest settings form

If a user does not submit the digest settings form on her profile, she'll get no digest emails.

On a site with 2 users, with only the second user explicitly subscribed and having an entry in {digests}, if the preliminary query in _digests_cron() is SELECT d.*, u.* /* We need the digests table first here, otherwise users with no digests row have uid = NULL in the results */ FROM users u LEFT JOIN digests d ON u.uid = d.uid WHERE status = 1 ; then we get 2 user results. However, if we take the whole conditional,

SELECT d.*, u.* /* We need the digests table first here, otherwise users with no digests row have uid = NULL in the results */ FROM users u LEFT JOIN digests d ON u.uid = d.uid WHERE status = 1 AND ( /* user is not blocked */ send_interval IS NULL OR /* user has not set their interval */ send_interval = 86400 /* user's interval is daily */ /* user's interval is weekly, and it's Sunday */ ) AND 1314123699 > COALESCE(last_sent, created) + (COALESCE(send_interval, 86400) - 43200) /* it's been at least (interval - 12 hours) since the last digest email */ AND ( 1314123699 /* NOW */ > 1314075600 /* SEND */ + timezone OR /* it's after send_time today */ 1314123699 /* NOW */ < 1314075600 /* SEND */ + timezone - 43200 /* it's more than 12hrs before send_time today, i.e. less than 12hrs since send_time yesterday */ OR timezone IS NULL /* the user has not set a timezone, fall back to the site default */ ) LIMIT 0, 250

Then we only get 1 result, and it's the user who has an entry in {digests}:

Sidenote, the query comments, while helpful, make the actual query harder to read. Could be better to have them not appear inline in the query.