Lardman,
I'll take your word for it on the italics thing.
As for the little white thing on the corner of the icon -- you're correct, it does mean a thread that you participated in. And, I swear, that this is a new feature -- I've missed having this indication that the old board software used to provide -- although I still feel that the old system's dot was more noticible.
Another thing I noticed today is that my unread groups don't get marked as "read" as soon as I visit the first group, so I wonder if ORG recently upgraded the board software...