He clearly didn't want to mention it, so why 'out' him?

I'm not sure he clearly didn't want to mention it - he didn't state he didn't mention it on purpose. I'm sure many people wondered, and going on LinkedIn is trivial. Had it not been on LinkedIn I wouldn't have looked further. If he didn't want to be outed, he could take Shopify off of Linkedin.

You could also comment the same on the 3 other comments that "out" him: https://news.ycombinator.com/item?id=42839195, https://news.ycombinator.com/item?id=42843755, https://news.ycombinator.com/item?id=42842682