what are the various icons that surround your avatar?
for example I have seen what looks like a man, and also a troll
some people have lots of stars, some have fewer, the stars are different colours
Stars increase as your level goes up. http://arduino.cc/forum/index.php/topic,50052.0.html#msg356979
If you like someone's post give them some love. If they are a spammer or a complete tool, negativeize them. In this way if you ask a question and get a response you can kind of judge their character/knowledge of the person and take that into account.
I can see what the rank titles are - even if they don't make a lot of sense (hierarchical-wise that is)
is Edison >> Faraday?
and what about Helmholtz?
Same as above. http://arduino.cc/forum/index.php/topic,50052.0.html#msg356979
and what's the difference between a big red + and a big grey + ?
Not sure what you mean. I'm not seeing the gray +. Did you mean gray -?
The + means there are new posts in that forum since you last visited. The minus means you've already been in there since the last post.