There is no reason why leaving a Revolve + in direct sunlight would damage it. It is, however, worth noting that the operating temperature for the speaker is 32 to 113 °F (0 to 45 °C) so if you are in a part of the world where leaving it in the sun could cause it to exceed these temperatures then it could cause some problems.
Also, as the speaker does have a seamless aluminum grill encasing it, ad metals do like to absorb heat nicely, you may find it hot to the touch if left for too long!
Let me know if you have any further questions!
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