my professional opinion is that the lines help discerning between events, too. but in case of the comments, they are competing too hard with the text. i would favor if the comments had no outlines:
the outlines for the events/conditions are not that harmful, because there is more room between text and outline; and the framing of the actions by the backdrop works fine, too.
if you were to drop all outlines, i figure you'd have to change the pastel color scheme and improve contrast to properly identify the events:
since this could possibly darken the mood of the event sheet and also impact its readability, i'd rather you do otherwise :)