Is there a way, perhaps via phpmyadin, a query that I can run, and which will subscribe authors to the articles that they are not subscribed with?
Try next query:
INSERT INTO jos_jcomments_subscriptions (
`object_id`
, `object_group`
, `lang`
, `userid`
, `name`
, `email`
, `hash`
, `published`)
SELECT DISTINCT `object_id`
, `object_group`
, `lang`
, `userid`
, `name`
, `email`
, md5(concat(`object_id`,`object_group`,`userid`,`email`,`lang`))
, 1
FROM `jos_jcomments` AS c
WHERE `published` = 1
AND NOT EXISTS
(
SELECT * FROM `jos_jcomments_subscriptions` AS s
WHERE s.`object_id` = c.`object_id`
AND s.`object_group` = c.`object_group`
AND s.`lang` = c.`lang`
AND s.`userid` = c.`userid`
AND s.`email` = c.`email`
)