Both the original and the printer’s manuscripts have ye after enter. The 1830 typesetter deleted this second ye in the passage. The omission was probably accidental, although there is the possibility that the typesetter noticed that the third verb, continue, did not have a ye and he therefore decided that the text would read more consistently with only the one ye at the beginning (thus “repent ye and enter in at the strait gate and continue in the way which is narrow”).
Even so, the occurrence of the ye after enter is correct. The language of this passage parallels the biblical phraseology in the Sermon on the Mount:
Jesus twice quoted this same language to the Nephites, and in both cases the ye is in the text:
Thus “enter ye” is appropriate in Jacob 6:11, and the ye should be restored.
As discussed under 1 Nephi 8:20, the adjective here is strait, not straight. Note, in particular, that the language of this passage is found in Matthew 7:13, which clearly refers to “the strait gate”, not “the straight gate”.
Summary: Restore the ye after enter in Jacob 6:11 (in accord with the reading of both manuscripts); all three Book of Mormon occurrences of “enter ye in at the strait gate” read identically and have the pronoun ye; as noted under 1 Nephi 8:20, the correct adjective for gate is strait, not straight.