This blog post was not written by Joel, nor does not sound like Joel. I think the comments are justified; the blog post feels quite abrasive to me. It's a little hard to put my finger on it, but the repeated distinction between work and vacation is a bit grating. Contrast this with a company like Netflix that don't count vacation days, and that assume that it their job to ascertain the productivity of their employees. I don't know, the whole post just doesn't sit 'right' with me. It's sort of "I bust my gut for you, I even try to work while I'm visiting with family, and you put me down for not having a room with a door that shuts and tell me I'm on vacation?!? (expletive deleted)" That's probably not at all how it is as Fog Creek, but that's the feeling I get from this blog post. Probably just unfortunate wording.
Yes. People sometimes spend too much time parsing tone of written text (hmm, I wonder why the OP talks about using video for face-to-face communication?).
I can't tell you how many times I've told people working for me to stop spending time parsing the tone of an email from a coworker or client and just pick up the phone and call them. Most of the time, any concerns with a poorly worded (or angry-sounding) e-mail are cleared up with a 2 minute conversation.