Chat issue

For 2 days now when I go to chat with a particular player in World chat I get message saying " Illegal Characters" only way to talk to this player is through private chat. No I can not get a screen shot cause pop up is only visible for about 1-2 seconds. Please advise how to fix this yest I tried restarting computer ,resetting page no change. isolated issue it occurs when I type players name ( Braless) and any variation of Thank you ( ty, tyvm included) I've been chating with this player for more than 12 years no issues until 2 days ago.