The watchers of this ticket may be interested in this post: Improvements to Browser User permissions (User Searchability by Project). Please add any questions or comments there.
 

I see what you mean 72cbdb0143d8 thanks for taking the time to explain that. I will change the link relationship from "duplicates" to "relates to".

I can see how they are related but it does not seem they duplicate each other. 

The other issue is to limit what is displayed to certain groups/roles. But personally I don't want to get the list of groups/roles and then scratch my head which of them should I use to limit the user picker list. How should I know which group to exclude to hide system users, like app users? 

I strongly urge to leave this ticket open or make it part of the requirement for the other ticket (explicitly elaborated in the description). Otherwise, we might end up with some fancy solution implemented in  JRACLOUD-36896 but not covering simple and obvious use case from this ticket. 

System users should be removed from the user list either by default or with some parameter but without messing up with groups or roles. 

I believe this issue is a duplicate of JRACLOUD-36896 – Limit User Picker to members of certain groups/roles in System Fields

I recommend that watchers of this issue vote on and watch the above issue. So that votes aren't split, I believe this ticket should be closed, but I will wait a week before taking any action in case anyone thinks both issues should continue to exist. Thank you!