I do not think that's a good idea because if several people are responsible, nobody feels responsible (see code review). See also T112679.
Workboard triggers etc exist to update assignees based on actions and phases of a task. Subtasks exist to split up work per person.

But it looks like someone already created an "Other Assignee" custom field in this installation...

I do not think that's a good idea because if several people are responsible, nobody feels responsible (see code review).

That's not been my experience on Github. On github when multiple assignees are used it can be a great benefit to people in need of a mentor by giving them a clear point person to ask questions and get help where needed. I contribute to OpenLibrary.org and we make a point of having an assignee (person who's doing the work) and a mentor (providing code review and support where needed). We seldom have more than two assignees.

See also T112679.

Haha well obviously I remain unconvinced since 2015 :)

But it looks like someone already created an "Other Assignee" custom field in this installation...

When I spoke to release engineering I discovered they were already using this for a similar purpose, and at my request have generalized it so we can experiment with it.

I guess this is already done at some point? cf. T329957#8625589

What keeps you from creating a Phabricator account called "Team Someting" with an email address that is a list or group alias? Then assign the task to that user.

What keeps you from creating a Phabricator account called "Team Someting" with an email address that is a list or group alias? Then assign the task to that user.

This wouldn't solve the issue we have which is typically we want to identify 2 people on any given task (for code review, pairing).

We have a custom "Other Assignee" field in Wikimedia Phabricator nowadays.

It does and that solves the issue we were having, but the main problem is this doesn't show up in the UI. I've opened a new bug for that:
https://phabricator.wikimedia.org/T329974

In T283746#8626141, @Jdlrobson wrote:

2 people on any given task (for code review, pairing).

But code reviewing isn't happening in Phabricator, is it? Maybe you would want to create rules for the reviewer-bot that automatically adds reviewers on Gerrit changes? That would be just an edit to that special wiki page and you would get that.

For more context, I am in a team which is not 100% developers. The information that a code is being reviewed is of particular importance to project managers, designers and program managers who don't use Gerrit (and shouldn't be expected to). A similar tool that's popular with product managers - Trello - allows and visualizes multiple assignees.