Several months ago I saw a large fast-food company's tractor-trailer with an image of a hamburger on the side. The image was scaled so that the burger was as tall as the trailer, probably ten feet or so. Near the burger, in large letters, was

Actual size*

In smaller letters, at the bottom (still quite legible), was:

*Not actual size

I believe delirium is accusing merlyn of doing the same thing. To paraphrase:

You're an idiot.*

*You're not really an idiot.

delirium asserts that merlyn really is issuing a personal attack. Whether merlyn means it as an attack (he obviously does not) makes it no less an attack. Whether delirium regards it as an attack makes it no less an attack. Whether there is a disclaimer makes it no less an attack. Whether merlyn had his fingers crossed behind his back makes it no less an attack.