To allow localized title tags for the moved paragraph indicators we need to introduce a placholder set in the C++ lib to replace it later on the phpside. The replace then would be done similar to the replacement for the localized line numbering.
Add a data attribute like data-title-tag="new" and data-title-tag="old" in the C++ output. This then will be replaced by the corresponding localized title="Click to jump to new location" and title="Click to jump to old location" in the moved indicator tags by PHP.
After the short discussion in https://phabricator.wikimedia.org/T180602#3771139 we decided on using the classes as indicators where to hook in the titles. The additional placeholder tags will be removed again then...