I find the date displays in conversations' history quite long, e.g. "[Mon 15 Aug 2016 18:07:18 CEST]". Maybe we could reduce the amount of characters ("[Mon 15 Aug 18:07:18]" could be enough if we use the local timezone), or add a setting "Displayed date format" that could be use for all "past" dates to be displayed (new messages are displayed only with hours and minutes, so this wouldn't apply to them). For me, the history date takes the half of the MUC panel (with roster on the left and occupants list on the right).