Comment 1 for bug 1670860

Mixin support should in itself will not cause side effects/bugs, so long as the modeling constraints are maintained. Now that users are only constructed via model code, this is no longer a problem. However, we are missing the ability to use this support.

This functionality was intended to support workflows, so that running a workflow could use some of this user's context. But we are some way from the actual implementation of workflows as a priority.