Interesting use case for multilingual content editing emerged for one of our clients: Their content editors work on gigantic material of translated and localised content. For Spanish speaking countries they've got over 20 localised versions of the site with some content shared and some content specifically localised. The same pattern reappears for other multinational languages, like English, French and German.
Their previous CMS of choice allowed for inheritance of "node translations", so Peruvian localisation of the site could inherit most of the content from Spanish and "override" the rest. They wanted to have similar ability in Drupal 7.
The team decided to use Entity Translation module to handle multilingual (obvious choice really), but no solution has been found in contrib ecosystem to allow for such inheritance and also meet some of their other specific requirements in this area. In the end we decided to build our own solution. That's how Language Hierarchy module was born.
The module is still under development while our client's site is in progress. It will be evolving with the site itself. We will be adding new features, requests and improvements. In the meantime, have tons of fun with it!