If it's an influential Mormon twitter, then I can see how it would make a difference. That's awesome.

I was just imagining a normal kid's twitter and couldn't see why that or some girl's instagram full or selfies and #outfitoftheday posts would be an influence.

Absolutely social media can and should be used for good. It's a very powerful tool, for sure. Sounds like your son and the admissions office recognize that he's put in the effort to make his social media use worthwhile. Good for him!