I'm sure they're thanking you for that feedback. Do you mind reopening that tab and giving it another shot? I'm sure they didn't purposely try to piss you off. It's a new product.
I didn't come to HN expecting sunshine and rainbows as a response--but it was nice to see. I'm not going to be shy about taking harsh feedback constructively. It seems people want an option for a reading/layout mode. Not hard to do.
His advice was valid, but his delivery could have been better. I guess it depends on whether he actually instantly closed his tab, or wanted to tell them he would have done that if he weren't trying to be so helpful right now.
The instant close-tab comment seemed like an exaggerated hypothetical response to a probably minor concern (assuming you're more than casually checking out the product) instead of a legitimate reaction. Because of that it came off as more mean than legitimately helpful, and meanness isn't the same as harshness.