Trivia: I took both the pics of him on his wikipedia page. https://en.wikipedia.org/wiki/Erik_Naggum
Yes, he could be harsh online, but he also had a sense of humor about the persona he had created for himself online. And it was a persona. That doesn’t mean he was tolerant of stupidity, or what he saw as stupidity, in real life, but face to face there was a passion and a sense of humor that got filtered away by having lots of infrastructure between you and him.
We disagreed on many things. Some of them, in retrospect, he was right about. And we had many heated discussions (mostly entirely in private - neither of us needed an audience to turn the heat up in a discussion). I remember him fondly, I miss talking to him and I was very sad when he passed. I still think about him.
His technical content was almost always high-quality, but one would often need to first don one's Nomex suit to get to said content.
Seeing his dual personalities was the first time I experienced this. It didn't bode well, that's for sure.