It all depends on the exact situations and the extent of the abuse. It can range from a few hours to a permanent block. Supervisors are usually more lenient with unregistered users and joint IP access. Permanent blocks usually come from the CA staff, not supervisors.
No, Supervisors cannot block another Supervisor. Only Community Assistants (Answers.com Employees) are able to block Supervisors. If you do attempt to block another Supervisor you will be presented with the following message "WikiAnswers Supervisors, Mentors, Senior Supervisors, and Community advisors cannot be blocked. For assistance contact WikiAnswers @ Answers.com"
Currently, you cannot block certain individuals from writing on your message board. You can block all Non-Supervisors from writing on your message board by emailing WikiAnswers @ Answers.com(remove spaces) and asking for them to do so. Please note that this will not block Supervisors or Community Assistants.
Based on the actions of the user, Supervisors decide whether or not to block by looking at past and current contributions, and Supervisors also receive advise from the other Supervisors and their Mentors. If the Supervisor sees many reasons to block the user, the user is then blocked.
Supervisors are able to block (ban) people from using this site. A block can be for as little as a few minutes to indefinite - depending on the severity of the user's actions. I have yet to actually block a user (although I have issued a few warnings).
Yes.
Regular contributors cannot disable a block on a user. Only Supervisors can disable a block on a user.
Yes, because they are supervisors.
You cannot block questions on WikiAnswers. Only Supervisors have the ability to get rid of a question, but there is no such action as 'blocking a question'.
To ban, you must be a supervisor. Supervisors have the ability to block, or ban, users.
There are guidelines which supervisors must follow if they are going to block someone. You will find nearly all users are blocked for a valid reason, and have continued nonsense even after official warnings.
Supervisors cannot be blocked though they can be demoted and then blocked. For this reason, it is impossible for a supervisor to block themselves.
You do come across idiots on here, but there are plenty of supervisors on this site who have the means to warn/block people like this and place in the correct answer you are looking for. As I will do now to the last person who placed the 1st answer.