The section about using ! and < to set options while logging in is really confusing, because it's all crammed together. My suggestion would be to trim it down like this:
For example, if the user exampleusername wants to log in, all of the following entries in the "Username" field are possible:
exampleusername (Log in, using default options)
exampleusername! (Log in, setting "Expiration" to "Never")
exampleusername< (Log in, setting "Bind to IP address" to "Yes")
exampleusername!< or exampleusername<! (Log in, setting "Expiration" to "Never" and "Bind to IP address" to "Yes")
The blank line between the colon and the first "exampleusername" sets that list of options apart better. Also, I don't think we need to say "Log in exampleusername" in all those places, as it can be assumed that putting a specific username into the login form will log in that username, and not some other one.
The bit about problems staying logged in can be removed, as that FAQ link should go in the Further Reading section. Some other Further Reading links I'd include would be:
What is the "Expire all my sessions" option when I log out?
How do I choose a secure password? How do I keep my account secure?
Why do I receive an "invalid cookies" error, and how can I fix it?