By all means feel free just to chat in the guestbook - as long as it's not spam!
Anybody with Admin below their name is definitely me or a trusted person. I myself will always sign as Butterfree. If somebody signs under that name but does not have the Admin label, it is most likely an impostor.
The last modified date is actually just the last modified date of the page template - so, since the poll results page template hasn't changed since February, it'll say that for every poll. Might be a smidge confusing for dynamic pages like the poll results, but that's what's going on there.
The poll results page says "Page last modified February 5 2016 at 20:02 GMT". Is that an error?