How to block users from advertising twitch ?

Ectar:   And again, we don't use the in-game notification for normal streamers. It's only really ever used for things like the major ESL tournaments/finals etc or special events/streams by Wargaming. It's not a regular thing you're going to see every day/week. This is done to raise awareness of the eSport side of the game where our target audience is the World of Tanks players and an in-game notification can reach over 150,000 players instantly.  It's quite common for players to have the stream active in the background listening to what is happening as they play World of Tanks or do other tasks.