#15

The reason diamonds aren’t used to make bulletproof vests is actually pretty straightforward. First, diamonds are extremely expensive, so using them in a vest would cost a fortune. Second, diamonds are much heavier than the materials typically used in vests, making them impractical and uncomfortable to wear.
The commenter in the thread wanted to explain this but didn’t know exactly how, so he jokingly said something like “1 gram is equal to 15 grams,” which is obviously nonsensical—and that’s what makes it funny. And hey, if you’ve read this far, you might as well follow me, because I explain memes and jokes like this all the time! 😉