This narrative passage begins in the present tense (have taken), then switches to the past tense (was, had done, did murder), but then returns to the present tense (have done, devour, do). The 1830 typesetter, John Gilbert, changed the last two present-tense examples to the past tense (devoured, did ) by penciling in these changes in the printer’s manuscript, yet he left unchanged the preceding present perfect form (have done) that begins the sentence.
Nonetheless, Gilbert’s changes to the past tense were never implemented in the 1830 edition or in any subsequent one. This use of the present tense in the original text provides a more vivid narrative, as if what has happened is happening right now. Such usage is referred to as the historical present and will be maintained in the critical text. For other cases where Gilbert attempted to smooth out shifts between present and past tense in the original text, see the discussion under 3 Nephi 28:3.
Of course, another possible emendation here in Moroni 9:9–10 would have been to change the past-tense portion of the narrative to the present tense:
Of course, the actual switching in tense is not that difficult for the reader to deal with. The fact that no printed edition has ever tried to eliminate this tense switching is fairly good evidence that there is no real need to emend the tenses here in this passage.
Summary: Maintain the shifting between the past tense and the historical present tense in Moroni 9:9–10, thus ignoring the 1830 typesetter’s two suggested changes to the past tense in this passage; such tense switching is not that difficult to comprehend and can be found elsewhere in the original text.