Is there any scope or interest in keeping track of closures and re-openings of pubs which are not in one's 'follow' l(area or individual pub) list?

We can see when new pub is listed through the tabs on the Activity page, and if you're lucky you see the Latest Activity entry on the front page.

How easy or difficult would it be to create a closure/reopening tab, or failing that, a link that shows all the 'Latest Activity' messages for the last day, week etc?

The reason for raising i is that when you look at the stats and features, they sometimes change without being able to see why. One example is the 'Pubs reviewed by county' numbers which change, but unless it's anew pub being added it's not obvious what has caused the change.