A minor thing...
I loaded a page while logged in, then left and came back later (leaving the page open). I decided to post a comment, but it turned out that my login had expired. Rather than presenting me with the option to log in, it simply reloaded the page – losing the comment box and adding a message at the top saying I was not validated to post comments (because I was no longer logged in). The problem here is that the comment I was going to post was lost.
Now, this isn't a situation that is likely to come up very often, but I would expect that if you try to do something that you need to be logged in to do, and you aren't logged in, it should present the log-in screen and then allow you to proceed with whatever you were doing.