It is rather odd that the posts are opened for comments for a few hours and then locked. If an Author wants to turn off comments for posts (which is the Author’s prerogative, of course), they can do so from the get go (right?), and it does not make much sense not to do it that way.
This leads me to believe that perhaps this is being done in error, like a system setting that was modified to deal with the case described above and then not set back. BB Posts are usually set to have comments up for exactly 5 days, but a changed value could turn that into 5 hours, perhaps?
These recent posts by Popkin were closed immediately, and then manually opened by Mark a few hours later. Is it possible that Popkin notified Mark, who opened the posts without realizing that the same thing was happening with his own posts?