Deleting a user won't permanently destroy any of that user's data (profile, chat history, etc) regardless of whether they were an admin or not. They will still show up in the user list under the admin section of the website and may be undeleted as necessary.
If you need a user fully removed from the system, you can contact support via our help desk: https://support.atlassian.com/servicedesk/customer/portal/32
...have mention name FirstnameLastname. Fe.: @MaartenCautreels This certainly helps to know who is being mentioned in a conversation. Imagine your colleague sends the following message...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs
We're bringing product updates and pro tips on teamwork to ten cities around the world.Save your spot