Similarly, I find comments where the single word "this" is used as an entire sentence detract from a forum based site. I can talk to u in allthememes! and sms abbreviations, but I chose to save that register for chat and look for something a bit more correct on forums. I readily admit that HN has been slowly trending away from that for nearly its entire existence.
Your comment about "this" and internet shorthand and memes is not related to your grammaticality judgement, unless you are admitting to conflating "clarity" with "propriety".
It probably wasn't the best way to phrase it and it's likely a losing battle anyway. I've found native speakers (which I believe the person I was responding to was) using this form more and more on boards such as this. Mistakes with uncountable vs plural distinctions are also increasingly common. E.g., "there's many reasons" instead of "there are many reasons".
As someone who spent years helping people with a variety of English problems including grammar, it's difficult to stop. I'll try to restrain this kind of comment to the articles themselves. There it's in the author's best interest to write in a way that doesn't cause the 30% or so of the population with stronger grammatical sensitivities to discount them.
What's your native language? Your English appears to be at least very near native.
Dutch, by the way.