[leephillips]

I think you're right that the authors knew exactly what they meant when they said "irony"; it's just that what they meant wasn't really irony (I make no comment about DFW, whom I haven't read).

"maybe irony is misunderstood as necessarily being obvious"

You aim for that sweet spot where about half your audience will miss your point. Socrates could needle someone in such as way that only his target was unaware of being mocked.

"our modes of communication are so shot through with the stuff that we can't just break down and communicate directly"

Again, I'm willing to take others' word for it that this is the world they live in. I'm just happy that I don't.