Here's a quick pass at analyzing the basic metadata for the online discussions.
I plotted a few calculated values (Excel pivot tables fracking ROCK, BTW...), to try to compare activity patterns. What's interesting in this graph is the average wordcount (green line) - low for the Blackboard discussion board threads (the left 5 items) and markedly higher for the 8 student blog (the right 8 items).
The number of posts in each discussion (dark blue line) is relatively consistent across all discussions. Slightly lower for the WordPress blog sites, but not dramatically so.
Also interesting is the red line - standard deviation of the "day of course" for posts. It's a rough estimate at how rapidly posts occur - a low standard deviation indicates the posts occurred relatively close together on the calendar. A high value indicates the posts occurred over a longer spread of days. This suggests that Blackboard posts were added in brief, rapid bursts, while the WordPress posts and comments were posted over longer durations. People kept coming back to blog posts long after they were started. Interesting. There could be a number of reasons for this - it's easier to see Bb discussion boards all in one place - and easier to forget to check various blogs for activity, etc... Or, do they just reflect more, and more deeply on blogs? Interesting... I'd love to find out the reasons behind the different values...
So... The WordPress discussions occurred over longer periods, using slightly fewer posts/responses, but with dramatically longer posts than was seen in the Blackboard discussions...