Here's the problem:
1) For most, if not all of our languages, the reverse-translate is simply not coded and is not always a 1:1 type of thing. There's currently no way to quickly and easily reverse-translate a string of characters written in a different language
2) Parchments written in-game in another language actually get stored in Common/English and forward-translated. They can be translated in-game because the original is always present.
I assume you're talking about messages written using the LORE web site and/or sent in through birds. In order to enable something like this, the LORE site would have to give you choices for languages (and know which languages your character could speak to avoid the sureity of meta-gaming) and pre-encode the parchments as they're done when using the quill in-game. Not saying it isn't possible, but it's extremely non-trivial, and we currently do not have anyone with the kind of time to devote to a project like this.