handshake icon means they joined within the last week. Take anything being said by someone with a handshake icon with an extra huge grain of salt, they might be legit but there's also a high chance that they're a shill trying to spread disinfo. As for the [S] next to someone's name, that means that they submitted the original post that the thread is about. If you however your mouse over these things you should see a brief description show up explaining what they are.