That may not be completely true for all all fora/BB software/plugins. I've seen instances on 1, possibly 2 sites where topics I expected to be 'marked as read' were left unmarked on a subsequent visit, the last post in each of the topics had been edited during/after my last visit to them.... an edit to existing threads does not cause the thread to bubble up to the top of the list ...
I fear we are leagues away from the battery problem now, did it get solved?