Consider this example:
a user signs up for twitch
they choose their username as barrycarlyon
When they are drawn in chat, their nick is barrycarlyon Twitch Chat will generally render the first letter of a name is as capital Barrycarlyon IRC will render as all lowercase, the chatters endpoint I believe will capitalise first letter also without a display_name having been set.
Since this user has not set a display name, then their display_name in tags will be blank (or in some cases depending on your parser evaluate to TRUE
So
- nick
barrycarlyon - drawn
Barrycarlyon - tags BLANK
Only when a user has set there display name in settings (or even just saved the first page) then and only then will display name in tags be populated with the correct name
So
- nick
barrycarlyon - drawn
BarryCarlyon - tags
BarryCarlyon
I run something like:
name = (display_name && display_name !== TRUE) ? display_name : nick
as my parser evals a blank tag to TRUE 