I mentioned this before, but I think mr_mischief explained it better:
The thick border between the byline and the node content followed by the thin rule between nodes reads at first as if you've used bottom attributions. It's very easy to miss that first by-line at the top and look at what is most clearly delineated. I'm not a fan in particular of bottom attributions, either, and I almost commented about that before I noticed it wasn't the intent. If you had used bottom attribution lines, that'd be merely a minor adjustment for people reading the site.
In the Others examining the Monastery section I would prefer to leave each username on its own line. When I am looking to see if someone is online (say ... luis.roca) it is much harder to see who is here in the dense paragraph format.