Is this really necessary? I think the "In other languages" boxes will become quite large...

People have been repeatedly asking for it, yes. If you have ideas for how to do this in a way that doesn't blow up the box too much I'd be happy to hear them.

How do I edit aliases in languages other than English then? The real problem is about not being able to add aliases *at all*, less about the layout of the box itself.

You can. You just need to change the language of the page using the Universal Language Selector at the top of the page near your username.

• This bug has been marked as a duplicate of bug 70033 ***

I'm still unable to edit aliases in the "in other languages" boxes. Are you sure this is a duplicate of bug 70033, which has been marked as solved?

Yes. It is not deployed yet.