Many themes and plugins allow users to enter texts, such as titles, footer, etc.
The user enters these texts via the admin pages and it's displayed in the site in different places.
This poses a problem for running multilingual sites. Static texts are translated via gettext. Pages/post contents are translated just fine using different multilingual plugins.
However, these texts are virtually untranslatable. There's just one version to show for all languages.
So different multilingual plugins came up with proprietary ideas on how to solve this. The problem is, we can't expect themes and plugins to support all these variations and cater to the needs of each multilingual plugin.
I suggest that WordPress include the basic mechanism for registering user inputs and then filtering it. Then, different plugins can hook. They will be able to get those values and possibly alter them.