No, I am not interested in becoming a Moderator. I would just like to know what are the functions of a Moderator, especially where it pertains to free speech?

My other question is whether or not a moderator on any individual forum topic has the ability to moderate on all other forum topics?

Moderators are assigned to specific forums - they can only moderate the forums they are assigned to.

Moderators are often viewed as a leader and/or expert in their forum. One of the main duties of a moderator is to edit or delete offensive posts or posts that are just blatant advertising.

Since the moderator is supposed to "police" their forum for activity that is contrary to the forum rules they themselves must make an effort to refrain from the same type of activity - moderators should be able to moderate degenerating posts without themselves getting involved in slagging other participants. A moderator by definition helps keep a discussion moderate - if a person has very strong views on most subjects and is willing to argue those views at every opportunity - that person would not be a good moderator for these forums.