I don't know the gerrit permissions model/system, But could we perhaps only enable it for a small group, so anyone that wants it would need to request access? That should reduce the risk level depending on how many people actually use the feature.

There has been runs since 2015: https://tools.wmflabs.org/sal/production?p=0&q=l10nupdate&d=

Do we need to rebuild identities (T77959#5055082) as well to pickup instances of usage before the account was created?

That is old gerrit vandalism that has been fixed, There was a problem with gerrit/phab replication that is now fixed so they are slowly flowing into diffusion.

I would prefer to see someone over prioritize a task so it shows up easier
(UBNs show up differently on IRC) and someone else with more experience
might see it and deprioitize as needed. Where as if it's not, it could
easily be missed.

Is ISA the name of the tool or Information Structured Additions? My main concern would be that ISA wouldn't be a descriptive project name in phab.

Maybe the question should be, If it wasn't disabled, why hasn't it been showing?

The simplest solution that already exists is that phab supports nesting subprojects, so you could have WMSE → 2020 → Wikipedia-in-Education-2020.

I suspect it may be related to T197083: Gerrit has created duplicate accounts for some users

Has this been reported/requested upstream (https://discourse.phabricator-community.org) yet?

In T215031#4921506, @Billinghurst wrote:

@Peachey88 is there a plan and/or timetable to migrate these other years to the other namespaces (for the previous years)? Just so we know what we are going to have to import from existing wikis, or not bother

Is this a upstream regression?

In T215031#4920932, @Billinghurst wrote:

The one thing that has been tumbling over in my mind is now that there is one wiki for many years, there will need to be the hierarchy to cover many years. In previous wikis, they could do it all one level down from root, and not have to worry about next year, that is no longer the case.

Will it be
2019/Schedule
2019/Volunteers

or
Schedule/2019
Volunteers/2019

or something else

If you do all at base level, then think that you can move it at the end then the relative links and link fixes are going to be awful, and prone to breakages. We can be looking to just have redirects at the base level so that each default redirects down, and that changes per year. Also could affect how templating is done, so it will need to considered early.

Checkuser is purposely disabled on beta due to privacy reasons, see T175197#3587005 and T104883#1431147