The original essay mentioned that people are often posting on social media about marrying their best friend, and this retort didn't address that at all. That is a trend that should be taken into consideration - it's not enough to say that long-term relationships can be built without looking into why they often are built on the basis of a friendship. It's a valid point that bonds of trust and understanding, as well as life events like births and deaths, can help couples build a strong connection, but the original essay sought to explore why it's so common for relationships to grow out of friendships - something which this retort failed to do.
Moreover, just because some couples may feel confident that their relationship will last does not mean that Nikhil's original skepticism regarding whether ten-year-old friendships could truly remain intact until marriage was unfounded. After all, people can be wrong about their feelings for someone now and find themselves in different situations ten years down the road. It is possible for couples to experience a profound connection now, but that does not mean that such relationships will be the same in the future.
Finally, it's worth noting that Nikhil's original essay contained a hint of humor - so in order to make a comical retort to the retort, let's make one more point: What if a couple got married despite having been best friends ten years prior and realized too late that they should have gone their separate ways? All we can do is wish them UrRong!