That question was exceedingly low quality, and to my eye looked to serve absolutely no purpose except to attack Shi'ite beliefs. Absolutely no research effort was demonstrated, and no attempt was made to explain why Ali's importance is in any way contingent on his being explicitly mentioned in the Qur'an. Almost half of the entire body is taken up by the greeting, which if I'd chosen to remove would've left naught but a single-line question. And even that single-line question was different on a rather fundamental level from what the poster originally asked.
If it were a recent question, I would've left a comment (as I did for the similarly weak question "Is “Mahdi” Fact or Fiction? Is he mentioned in the Quran?" which follows similar patterns) and given the poster a chance to fix it, or at least learn from their mistake. In this case, however, the question was more or less abandoned for over a year, and the user who posted it apparently hasn't even logged in since, I didn't feel that leaving him a comment explaining my action was necessary.
Given the low quality of the question and the fact that it I felt that it really had no value on this site I chose to delete it.