Status update (3/30): So only one server overload in the last three days. That's great news. We fixed more permissions issues today — you should be able to see (and borrow) items outside your own group(s) now. The spontaneous taxonomy term cloning is history, and images should all be available again. We still have work to do on the media browsers within item forms, but we're watching new content come in and things are starting to look pretty solid. We're aware that there are HTML codes making their way into client sites again — our first attempt to fix this wasn't quite right, but we should have a new solution tomorrow.
If you have issues you want to see addressed, the Mercury issue queue is the best place to go. You can follow issues and see when we have updates or solutions. If you have an issue that is not already the queue, you can add it directly there or email firstname.lastname@example.org. Our apologies to anyone who has been submitting issues to the support request form and wondering why we weren't responding—the site was not sending us emails about these.
FYI: If you created an item recently and noticed keywords or other tags have disappeared from it, this was a side effect of fixing the issue that was causing taxonomy terms to spontaneously clone themselves. You might need to re-add the missing tags.
Drupal 9+ Mercury Reader users: Eric Neville solved some issues with the reader module. Grab 2.13 asap (Composer should pick it up).
Drupal 7 Mercury Reader users: Michael Sheldon was kind enough to patch a number of issues with the Drupal 7 version of Mercury Reader which caused it to be unhappy with the new system. The new version is available here: https://github.gatech.edu/ICWebTeam/hg_reader-7.x/releases/tag/v2.20