This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
Users can no longer opt-in for "public" edit history
if site owner disables it.
This feature adds cost and complexity to post rendering since
user options need to be premeptively loaded for every user in the
stream. It is also confusing to explain to communities with private edit
history.