It happened to me already a few times that i posted (suggestions of) team strategies with the box 'teammates only' toggled 'off'. I really don't know how this can happen. I'm sure i did not deliberately toggle this box. Now, can it be possible to ask for confirmation when submitting a public message in a team game? Or maybe separate the public chat from the teammates chat?
I think that separating the chat into team and public is a great idea in team games, and have suggested it myself.
However, I am not so certain about a confirmation being necessary. I have not had this problem myself in the team games I play since I never uncheck that box until the game ends. Perhaps clicking "enter" for submit instead of the button would help avoid the issue; I do see it happen every few games on the other team.
Add a button that allows you to delete a posting that has been made in error. After all it's possible here, in the forum.
Although that should only be available for the last message in the chat window. Otherwise confusion would set in if; playerA says something playerB responds playerA deletes leaving playerB's statement looking odd.