Isaiah 29:14–15 (King James Bible) for the wisdom of their wise men shall perish and the understanding of their prudent men shall be hid woe unto them that seek deep to hide their counsel from the LORD
Oliver Cowdery initially wrote but in the printer’s manuscript, but he later altered it to and (written as an ampersand) and with heavier ink flow. In the original text, there are 7 occurrences of “but woe” and 12 of “and woe” in sentence-initial position, so either is syntactically possible in 2 Nephi 27:27. The correction here looks much like the again that was supralinearly inserted earlier in verse 22 of this chapter. As with that insertion involving again, the correction here in verse 27 probably occurred when Oliver proofed 𝓟 against 𝓞 (which is no longer extant for this part of the text). For further discussion of scribal errors involving mix-ups between and and but, see the list provided under 1 Nephi 8:20 (in the discussion regarding straight versus strait).
Summary: Retain in 2 Nephi 27:27 Oliver Cowdery’s corrected and in 𝓟; this corrected reading (and rather than but) was probably based on the original manuscript, no longer extant here.