WHy can't I use Shop etc while in Leaver Buster Queue?

They really should at least let you use the chat bar while you're in low priority.

The client doesn't actually mark you as "In Queue" during the low priority countdown, so any friends who don't know you're waiting for it can message you and you can't respond to them at all without closing out and resetting the timer.

Maybe keep the sidebar disabled so you can't start conversations, but at least let you respond to anyone who does message you during it.