Looks like compatibility hacks for various websites.
Interventions - are deeper modifications to make sites compatible. Firefox may modify certain code used on these sites to enforce compatibility. Each compatibility modification links to the bug on Bugzilla@Mozilla; click on the link to look up information about the underlying issue.
User Agent Override - change the user agent of Firefox when connections to certain sites are made.
https://wiki.mozilla.org/Compatibility/UA_Override_&_Interventions_Testing
Northern Conservative Fundamentalist Baptist Great Lakes Region Council of 1912.