If you are using a recent enough version of Moodle, then go to Users -> Permissions -> User policies, and you can show which user columns are shown in user reports.
(If City is not an option there, then you can set it by hard-coding the setting in config.php.)
The quickest way to get your messed up MOODLE_23_STABLE branch back to origin/MOODLE_23_STABLE is (assuming that you are on your MOODLE_23_STABLE branch) to do
git reset --hard origin/MOODLE_23_STABLE
Note that that will remove any uncomitted changes that you have, so you should probably start with
git status
If there are changes you want to keep, then do
git stash
git reset --hard origin/MOODLE_23_STABLE
git stash pop
The event that triggers the email to be sent is when the quiz is submitted, which is either:
The email is actually sent the first time cron runs after that event.
This is exactly the sort of analysis and thinking that is needed.
I am afraid I have not read through all your analysis in detail yet. (I am, technically on holday at the moment.) but I will read it properly when I get back.
Two things I have concluded so far:
1. To satisfy all the sharing (and then re-editing) use cases Moodle should support, we need some sort of simple versionning scheme. In order to be simple enough, I think that means versionning like wikis, not versionning like git/github, but I might be wrong about that.
2. If we are really trying to solve sharing, then I think the solution should encompas not just sharing within one Moodle site, but also allowing different teachers from different schools to collaborate on a question bank, for example on a Moodle community hub. At least, the mode should be robust and general enough to support that, it would require the admin to enable it, probably.