As part of T353225: Echo: Make use of conditional user defaults, I need to delete entries from user_properties that match their current (conditional) default. While it is possible to delete such rows by doing something like mwscript userOptions.php --wiki=enwiki --delete --old 1 --fromuserid=906 --nowarn 'echo-subscriptions-web-article-linked', this has a couple of issues:

• it is incredibly easy to mess up,
• it is impossible to run via foreachwiki, because --fromuserid is specific for each wiki (based on the cutoff date from the conditional defaults config and the lowest ID among users who registered after that date)

To resolve those issues, we need something like mwscript userOptions.php --wiki=enwiki --delete-defaults 'echo-subscriptions-web-article-linked'.