Handle display name changes discreet
Show display names as they were at the time of sending
Don't show a state message when a display name is changed
When a display name is changed, show their previous name as a suffix after their new name in the first message under that new name. For example:
Wilko (previously Rens)
When looking at members, show (previously X) for 24 hours after the person has seen the display name change (either in the member view or chat view).
If a person changes their display name in just one room, show this name, but show a suffix of the name the user may be most familiar with (the name used in most rooms). For example:
W. Manger (Wilko)
Where 'W. Manger' is the local display name and 'Wilko' the display name the user has in most other rooms.