See rationale on bug 52723 comment 37, counter argument on comment 39, response to that on comment 48.
This feature was removed in https://gerrit.wikimedia.org/r/#/c/78047/.
There are two different ways we can do this:
- Add a new user-right called 'massmessage-global', and require users sending notifications cross-wiki have this right.
- Add a config switch ($wgAllowCrossWikiMessages) that allows that wiki to send messages to another wiki. So this would be turned on for meta, and any user on meta with 'massmessage' would be able to send cross-wiki.
Personally I favor the user-right implementation since it gives more control and flexibility, but at the same time, it adds yet another user right >.>
Next question: what should happen if a user attempts to send a message to a list with cross-wiki targets but does not have the proper permissions (or it is disabled on the wiki)
- The entire submission is rejected until the spamlist has those entries removed
- A warning is given to the user and those cross-wiki targets are dropped from the list.
- If we use the config switch, the parser function could reject any target that is not on the current site with the red error message we have for invalid input.