Note: T21 publishes the hosts guide so that members can comment and so everyone can see what it is the hosts are trying to accomplish :)
The primary goal of T21's hosts is to encourage and facilitate active and interesting discussions and a sense of community in Tangent21's forums. As a function of this goal hosts will sometimes need, in extremes, to delete, move, suspend or edit topics, but this isn't their job. The job of a host is as an enabler, and as a supporter where necessary.
Hosts may edit, suspend, move and delete topics and posts in extreme circumstances, but in most cases this should be viewed as a failure of other means (there are obvious exceptions where swift action may be required and other means a waste of effort - we trust Host discretion in these cases). Hosts should attempt to finesse discussions back onto topic and should move any necessary cross-conversations off the forums, except where it is necessary or vastly more expediant to deal with the case in a public manner (again we trust Host discretion).
In all cases posts should be suspended from public view rather than being deleted and where reasonable members should be emailed and decisions explained. This follows directly from the definition of hosts as enablers, and their powers as functions of this goal, rather than as enforcers.
As a primary rule, staff will not enter discussions about staff decisions on the board, but where a member has valid complaints or concerns the Site Admins (email@example.com) can arbitrate and act as necessary.