Here the 1874 RLDS edition accidentally replaced the past-tense came with come. This is an obvious typo that was removed in the subsequent RLDS edition (in 1892).
Also note here the placement of the prepositional phrase by night at the end of the passage. Without the appropriate punctuation, one would tend to read by night as stating that the destructions came by night. Yet in the book of Ether, battles (unless otherwise stated) are always fought during the daytime. Consider, for instance, the series of final battles in Ether 15:15–26 where the two armies battle in the daytime but at night rest and prepare for battle on the following day. There is only one battle described as occurring at night (and explicitly mentioned as such in Ether 8:5: “they did give battle unto him by night”). So here in Ether 13:14, Ether goes out by night, during the lull in the fighting, to observe what has happened. In fact, this is precisely what verse 13 states: “and he hid himself in the cavity of a rock by day / and by night he went forth viewing the things which should come upon the people”. So in verse 14, in order to show that by night modifies viewing and not came upon, the 1920 LDS edition placed a comma before by night. The critical text will also adopt this distinguishing use of the comma. For other examples of displaced prepositional phrases in the text, see under Mosiah 26:23 (or, more generally, under displaced prepositional phrases in volume 3).
Summary: Maintain the comma in Ether 13:14 that separates by night from the immediately preceding relative clause, “which came upon the people”.