Autocomplete does not fill in users not part of the current project
Our organisation uses the 'Internal' model where every user can access every project. I would expect this to function internally as everyone being 'Reporter' in every project, but it doesn't in several places. Particularly I cannot mention an 'outside' user easily in an issue - typing @ does not suggest any usernames not being an active member of the project, even though they'll be able to see the issue and receive the mention.
Semi-related to #19668 (closed)