How does the Duty Finder language setting ACTUALLY work?

So, I play on Midgarsormr. NA Server.

Recently I have been reading about people saying they get shorter queue times if they select E only, which just greatly confuses me, because I've always assumed being willing to play in any language using the JEDF setting would make it faster for me.

But it made me think that it actually depends on how the setting works.

So.. What does it do?

1. If I select JEDF, will it first pick a random language, let's say F, and then force me to wait for other people who have also picked F, or perhaps also JEDF?

2. Will it only pair me with people who have the exact same JEDF setting? If so, are there more or less people using JEDF than only E?

Choosing JDEF team you with people who crossed J, or E, or D, or F, or J and E, or D and F, etc
Crossing only E will team you with people who crossed E, but those people could actually have crossed DE, JE, FE, JDE, JFE, JDFE, etc

If you are paired with a J lets say only 5/8 are in this q, you could be stuck in limbo if no other j language people are selected

Basically, what these replies are telling you is that what you were told is wrong. Or at least misinterpreted.
Selecting E only will not increase queue speeds, but limit them.

Logically speaking, if you're playing on an English data centre and only select J, you probably won't be seeing speedy results. So if someone told you "Hey Kat, you've got J selected. You should select E if you want faster queues!" this isn't them saying E only. If anyone actually told you this is up to my imagination as I'm sure I'll never know for sure!

Warning: this is my understanding based off of how the queues work with Frontlines and PvP.

First off, each Duty has a different queue set, each queue set is subdivide into 4 "language" sub-sets and each sub-set is subdivided into parties.

The 4 "language" sub-sets are J, E, D, and F. By activating/deactivating the language selector you are determining which language sub-sets you are allowing the server to put you in.

Parties are determined by content type:
4 man content parties are [T][H][D][D].
8 man content parties are [T][T][H][H][D][D][D][D].
post-LotA 24 man content parties are [T][H][H][D][D][D][D][D] with LotA using standard 8 man parties.
Frontline PvP parties are [IF][IF][IF][IF][IF][IF][IF][IF], [MS][MS][MS][MS][MS][MS][MS][MS], and [TA][TA][TA][TA][TA][TA][TA][TA].

When you push the Join button in the duty finder what is really happening is that you are telling the server to put you in the oldest open slot for whatever you are queuing for that is available in your selected language sub-sets. If their is no open slot it will create a new party and place you in that party. Every so often (~3 minutes I think) the server will check if players have abandoned the queues and then rebalance to fill any holes using a oldest queuer oldest slot mechanism. Between these rebalances, new queuers are put into the oldest open slot.