(I just realized this is the wrong section, this was notices on the Windows client, sorry.)

Update: there's more to it. Nba YoungNaijj vs BP renew.
We did chat during the game. He said "The luck" at the very end, the observer left the game, and then I couldn't click anywhere to enable the...

I would expect people to just not see the messages, but not preventing me from entering anything. But now that I think about it, it does make sense...
I ran a few inconclusive tests. My best guess...

Ok actually it's not only linked to Nathanias. See N0RUBBERZ vs BP renew.
I did manage to chat for a while, and later it seems to get disabled. And I did chat while having Nathanias on the board, so...

I've noticed this a few times when I wanted to say "gg" before giving the finishing blow. The last time, it was after playing Nathanias: clicking on my of my opponent's "picture" to enable the chat...