It has become more commonplace to use lowercase id and class names in CSS especially as dev tools don't use them at all which created an issue in this bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1325505 This also came up with linting the test pilot experiment. It would be neater all round to make them consistent with others. All classes and id's starting with "userContext" should be probably be changed to "user-context" or "usercontext".

Bulk change per https://bugzilla.mozilla.org/show_bug.cgi?id=1401020