I have learned from being distracted when a black chat message flashes across the screen and realizing that I must've done it to others myself, that if you have a message to "everyone", especially about the song being sung, you wait until right after the song is over and applause is being given to post it so that nobody's stride gets broken midsong by someone telling you how flawless your performance is. People can get a quick chance to enjoy all the comments on a song at once, unless you have a long scholarly post and then you can post it at the next song break.