[[MediaWiki:Tog-noconvertlink]]

The /qqq states that this is an optional message. It shouldn't be, right? I understand optional messages as those that normally don't require translation...

This one falls in a very special category. It is only used in wikis with variants. Because of that it was decided to mark it optional.

Oooh, I see...

I seem to be able to edit the English original message (I didn't save, but still...). That shouldn't be possible, right?

Sure you can, but you just shouldn't.