==== Motivation
For IP Masking MVP we want to keep the experience for temporary users as consistent as possible with the current experience of unregistered editors (with the exception of Notifications). This is so that we don't introduce too many major changes all at once. In the post-IP Masking MVP future these changes can be re-evaluated.
==== Spec
* Temporary users should not been able to set user preferences
** Disable access to //Special:Preferences// - done in https://gerrit.wikimedia.org/r/c/mediawiki/core/+/778685
** Disable preference setting via the API - T330815
** Update UserOptions classes to treat temporary users like anonymous users - T332416
==== Notes:
* This is a follow up from {T326759}
* Editing and Web team rely on cookies for customizing preferences for unregistered editors. They will continue to use the same mechanism for temporary accounts in the future.
* Size of the user_properties table is also a concern: {T54777}