Changing user name after chat is loaded goes trough different checks like duplicate user names inside single chat room, reserved user names check etc… When chat is first loaded I had to ensure that no duplicate names exist without running any special checks and using login name was obvious and gave most performance because chat doesn’t have to query database when setting initial user name.
I see that the feature of using nicknames is very important so I’ll change this behavior for the next version. Until then you don’t need to use special Javascript hacks, just change
$this->user_name = $current_user->user_login;
from line 245 of quick-chat.php v4.10 into
$this->user_name = $current_user->display_name;
But to make all features work fine make sure logged in users do not use same display names. In the next version I will make display names used by default and do the checks when deciding on initial user name so all will be fine.