Community owned posts do not generate any reputation for the owner, have a lower reputation barrier for collaborative editing, and show only a revision history instead of a signature block.
It is agreed that the main point of CW is editing, not avoiding reputation generation. The tooltip needs to set its priorities straight then!
Proposed rephrased replacement:
Mark an answer Community wiki to encourage users to edit it. The reputation barrier for editing will be lowered for this post; however, you will not gain any upvote reputation from it. This cannot be undone.