This page documents a Wikidata policy. It is a widely accepted standard that all editors should normally follow. All changes made to it (except for minor edits such as fixing typos) should reflect consensus. When in doubt, discuss your idea on the project chat.
This page in a nutshell: Do not make personal attacks.
The higher up on the pyramid everyone stays, the better off everyone is. The top three sections are the ideal.
Do not make personal attacks anywhere on Wikidata. Comment on content, not on the contributor. Personal attacks harm the Wikidata community and collaborative atmosphere needed to create a good knowledge base. Derogatory comments such as name-calling may be removed by any user. Repeated or egregious personal attacks may lead to blocks.
