Flock is still in the pre-release developers preview stage, so it isn't surprising that everything isn't yet working as it should.
One of those things that isn't working on my system as I would expect it to is the newly-renamed "My News" function. With it you can subscribe to a site's RSS feed and receive notification, via a change in color of the My News icon on the icon bar (from white to orange), when the feed is updated. Once you've read the feed, you can (in theory) mark it as read and thereby change the bold font displaying the feed's name in the sidebar to a normal font. That's the way it is supposed to work at least.
For the last several builds, up to and including this morning's build — Flock 0.7.0.6.1.0 build_id: 1147073320.4097, marking the feed as read has no effect on the characteristics of the feed in the sidebar as is illustrated by the screenshot.
I've begun downloading a new build of Flock each morning just to see whether the previous potholes I had encountered have been patched. So far the My News feed problem hasn't. However, I was pleased to see that another problem (bug #1577) that has existed in both Firefox and Flock for some time appears to have been fixed. So potholes do get patched, and I'm sure that the one for this minor annoyance for My News will be fixed too eventually.
I knew when I embarked on this journey of testing Flock "there'd be days like this" so I'm not too concerned about this bug. But posting my comments about it here gives me a chance to elaborate on it a bit more than I can when posting a bug report and it gives me something to talk about on my blog. Hence my comments this morning.