I thought Dawn's point was just a sarcastic jibe? (With the ameliorating wink-smilie, of course. I often wonder whether a court of law would reduce the sentence for a variety of crimes if it could be shown that the perpetrator left a winking smilie at the scene. So, like, he didn't really mean it nastily or anything.)
Anyway. The point about Dubliners is that it showed that Joyce could write in a straightforward style before he branched out. It's nothing to do with show/tell, and I was using it in support of Holbrook's point about general rule-following. For the record though, many of the stories where Joyce predominantly tells are first person narratives, or directed third person narratives, where we're seeing the action through one character's eyes and telling is not only permissible but more or less essential. In true omniscient narratives, such as Two Gallants, A Little Cloud or his most celebrated story The Dead, there is a good deal of showing through dialogue and activity.