The same thing happened to me.
1. June 3rd.
2. Didn't test other chars on the same account. I could use chat as normal on other accounts.
3. Don't have other pc.
4. Happened only once.
5. No, just made a report. At first they told me it was fixed, but it wasnt so i msg support again. After the 2nd report which was 2 days later they fixed it.
6. Windows 10 Home.
PS. It also happened to few other clan members (MorningStar - Chronos) we just thought its some kind of new chat ban we receive after being mass blocked in game.