Instead of deleting the opinions of ''others'' (apart from obvious WikiVandals), try to incorporate it. You are always free to delete your own content, though note that it may not be good for everyone else to do so.

Every addition should be seen as a message from the "collective consciousness", however poorly worded or organized.

''Unless it's the addition of a message from an individual, like this one. :-) ''

Everyone is free to ''add'' content, but once others have viewed it, their personal WorldView is now affected (you've collapsed their wave function!). Now you have to keep it, until the CreatorAsOwner deletes it, or refactor it into the discussion.

The other ''caveat'' to this is that if there is an ''absentee'' "landlord" of a WikiPage (no views for 120 days?), then others should be able to delete content.

The true sign of a WikiMaster is that s/he can reduce a messy page to a much shorter, well-organized one without losing a single point.
--------
See also: WikiFilterist, LessIsMore, WikiReductionist