What are taboos within a wiki community? 

* to fake an identity (use the signature of another author) (IdentityTheft)
* to fake a communication (change the semantics of a signed contribution of another author) (Wiki:DisagreeByDistorting)
* to insist on questioning community values as a non-member of the community
* to insist on certain content without seeking consensus (EditWar)
* to insist on insulting or aggressive behaviour

People who violate one of these taboos can not be part of a wiki community (see CommunityExile). The reasons should be obvious and are quite similar to real world communities: the behaviour is either illegal or damages the community in some way (stability, reputation, respect, trust, cooperation).