> ah right, judging someone from grammar is a very rational thing to do
I think you just turned "rational" into a label. Apart from your attempt at sarcasm, this statement is probably true. Like it or not, your ability to structure sentences reflects your ability to structure thoughts.
I agree, up to perhaps a log-log scale. My grammar isn't likely to be significantly better in 30 years. However, when comparing among groups with similar English experience, grammar is likely to have a reasonable correlation with well-structured arguments. Also, the amount of time since learning English is not under your control; adherence to the rules of grammar is.
Perhaps more importantly, it wasn't actually grammar that I criticized. It was erratic use of punctuation (which was clearly for effect and to catch attention rather than clarity), lack of appropriate capitalization (which negatively impacts readability, and definitely doesn't require extreme English skills to get right), aggressive tone (which I find annoying pretty much anytime I see it on the Internet, as it provides no value), and sounding like a self-righteous teenager (which everybody older than ~24 finds irritating). Though one could argue that capitalization and punctuation are components of grammar, I used specific terms rather than a general one for a reason. I tend to be quite forgiving of grammatical mistakes that can be attributed to native language differences and different levels of skill with English. But, I'm less forgiving of things that are very easy to control and get right, even for non-native speakers, and that negatively impact my ability to read and understand. When wrapped in negativity and an aggressive tone, I tend to feel negative towards the person. So, I explained why his tone made me feel negative towards him, and why I thought people were voting him down.
I thought I was providing a helpful suggestion for how he could better present himself and his ideas on HN, but one can only do so much to be helpful.
I think you just turned "rational" into a label. Apart from your attempt at sarcasm, this statement is probably true. Like it or not, your ability to structure sentences reflects your ability to structure thoughts.