Erm, yeah, I was wondering about that. Keeping in mind that I'm a US'n and thus irony-handicapped, could anyone tell me if my assessments of his examples are correct?

Underlying meaning: That was a stupid thing to do.

Ironic expression:
“Oh, brilliantly done.”
“Aren’t you the clever one, then?”
“The stupidest act in human history.”

“Oh, brilliantly done.” strikes me as sarcasm.
“Aren’t you the clever one, then?” seems like irony.
“The stupidest act in human history.” is a flat-out insult.