I think Wiki Answer locks can be usefully applied to questions that have attracted a list of answers, and become popular, before anyone realized their poor fit to focussed Q&A.
This is where they can be set by Moderators.
However, I struggle to find any detailed description of them.
On GIS SE Meta a question has been asked about who can edit Q&As which have a Wiki Answer lock (Who can edit locked CW posts?) and I am not certain of my answer to it.
For a Q&A with a Wiki Answer lock:
- Can anyone besides Moderators edit the question?
- Can all of the existing answers be edited by users with the edit community wiki privilege at 100?