The DMFI language tool mostly operates as a substitution cipher. Each letter that gets typed into the tool is replaced by one or multiple letters/characters. This creates an effective illusion of a foreign language—something which players cannot read. It also gives a good sense of the general character of the language by how the cipher is set up. Is a language vowel heavy and flowing or guttural and clipped, etc.
In addition to the substitution cipher, there is also a look-up table which replaces some whole words in their entirety. Here is an example in Elven. 'Hello' gets translated to 'Alae', while the individual letters would actually make up 'Iracce' via the cipher. This is well and fine, as 'Alae' is the correct lore translation.

Problem:
The problem begins, when that look-up table translates worlds into IRL languages. The biggest offender that I've found is Illuskan, but I'm sure there are others. Here is an example:

This is obviously just German, which is a problem on three levels:
1. The language tool is using a simple look-up table. There is no remote attempt at grammar. No conjugation, declension, adjustment of word order, etc, etc, etc. It is like nails on a chalkboard for anyone who actually speaks the language being subjected to this barbarity.
2. Even given the butchered grammar, speakers of the IRL language in question can often get an unfair OOC/meta advantage in being able to interpret the untranslated language. While the above example is a grammatical mess, it's still clear what is meant. Even Google Translate can figure it out.
3. It is a violation of established lore. There simply is no one-to-one equivalent between Forgotten Realms and IRL languages. Amn and Cormyr—the Spain and France of Faerun—both speak Chondathan (Chondathan doesn't appear to use a look-up table to either language, and is just a cipher). While Illuskan is described as being inspired by 'North Germanic', the three actual lore translations we have are far more Norse. Dock-Alfar for dark elves comes from the Old Norse dökkálfar. Hamfriggan and Eigerstor are the remaining two words given in lore. Only 'Eiger' sounds more German than Scandinavian.
Solution:
Simply remove all instances where a look-up table translates whole words from an FR language to an IRL language. Every language has a substitution cipher at its core, and if these words are simply pulled from their respective look-up tables, the cipher will take over and the problem will be solved.
For languages like Elven, Drow, and Alzhedo where we do have an extensive lore dictionary, whole-word translation is appropriate and good.
In terms of actually implementing the solution, I imagine that would just take going through some text file and deleting things.