where is the wikimedia config(s) for "which types of notifications are enabled by default, and whether web/email/both." ? I'm particularly interested in: 1) which types do not get sent by email (by default), and 2) the configuration variants between "existing vs new editors".
$wgEchoDefaultNotificationTypes (which are available, e.g. 'Email from another user' does not let you get email notifications when you receive an email. The film ''Inception'' depicts what occurred when this malfunctioned).
$wgDefaultUserOptions["echo-subscriptions-...] (enabled by default, web, email, both, neither, etc.).
If you also want to know which can not be turned off (e.g. edit-user-talk is mandatory for web), no-dismiss on $wgEchoNotificationCategories
AddNewAccount/onAccountCreated for the variants between existing and new.
There is only one I could find that is Wikimedia-specific (as opposed to anyone with the extensions), thank-you-edit (the milestone notifications), due to to the bug.
It's disabled on web (and was never available for email (why, will file that?)).
I guess it's because you're on the site anyway, you know you just edited, and it could be considered spammy?
Although you could make the case it's good for re-activation and not too spammy since it's rare.
if you file a task I or someone else could make a script to present all that in human-readable form (good in case we change it).
Some of those seem to be in https://phabricator.wikimedia.org/diffusion/ECHO/browse/master/Echo.php
Some (and Echo configs) seem to be in (Warning, BROWSER FREEZING LINKS, even in github without the syntax highlighting) https://github.com/wikimedia/operations-mediawiki-config/blob/master/wmf-config/CommonSettings.php and https://github.com/wikimedia/operations-mediawiki-config/blob/master/wmf-config/InitialiseSettings.php
A good result would be
- updates to https://www.mediawiki.org/wiki/Extension:Echo#Configuration and
- automatic generation of the details Matt explained (Wikimedia-specific current config) in another page/location.