this player's name is _inevitable
but in chat window a different name appears
How?

[You must login to view link]

Hi,

You can see in the news feed of ColdHardCash that he changed his name very much:
http://www.voobly.com/profile/view/79383

3 September
ColdHardCash has changed his name from Noctred (11:12 am)
ColdHardCash has changed his name from ColdHardCash (11:11 am)
ColdHardCash has changed his name from kibitzer (11:11 am)
ColdHardCash has changed his name from ColdHardCash (11:11 am)
ColdHardCash wrote on Lord_PAGAN's wall (10:20 am)
ColdHardCash wrote on [ZGEN]Z_Cabel_GEN's wall (10:15 am)
ColdHardCash wrote on fumikey's wall (10:11 am)
ColdHardCash wrote on Praxes's wall (10:07 am)
ColdHardCash has changed his name from itsInevitable (9:02 am)
2 September
ColdHardCash has changed his name from ColdHardCash (11:33 am)
ColdHardCash has changed his name from _inevitable_ (11:33 am)
ColdHardCash has changed his name from ColdHardCash (7:49 am)
ColdHardCash has changed his name from _inevitable_ (7:48 am)
ColdHardCash has changed his name from ColdHardCash (7:48 am)
ColdHardCash has changed his name from in3vitable (7:47 am)


You can see he switched a few times from _inevitable_ to ColdHardCash.

Most likely, he changed his name on the website, but didn't log out and in again on the Voobly client.
(You can call this a bug, Voobly should force a player to log out and in again if the name is changed).

Same thing can happen if 1 of the 2 names is a premium account, you can log in with 2 accounts if 1 is premium, but if the player with 2 accounts logged in sends a message to someone else, you see the message coming from the name he is logged in with his Voobly client.

Off topic:
Members who change names very much do it for a reason, and usually, the reason is nothing good i.m.o...