I believe you already asked about abbreviations
here and you will find answers there, because I'm too lazy to type them all out
As for people disappearing... well, if they only have GB in one window, they might be moving between forums, or between SYM and their PM box, so they will still be on GB but won't appear on SYM. Especially if there isn't much happening on SYM, people probably go and check out the other forums.
Then there are those of us who lurk and don't appear at all...
Edit: I don't know anything about posting polls, sorry.