First the good news: our Spring Release is progressing at a steady pace.

Pretty pictures mean things are going to be alright.

However, it is time to announce a change we are going to make to vanilla dialogue.
Tamriel Rebuilt, as a province mod, has rather unique needs and encounters problems that most mod creators can safely neglect and that users do not need to know or care about.
As such, things are going to change in the next releases of the mods which are dealing with this problem (Tamriel Rebuilt's Spring Release, the upcoming Province Cyrodiil and Skyrim Home of the Nords releases, and Patch for Purists 3.0).

This is one of the cases where neither is really true. The problem affects every user (although few are aware of it) and several more mods. Yet, it is a problem that's only sometimes fixed, often fixed incorrectly, or something that's considered a quirk and not a serious bug.

Picture this: your Nerevarine newly vanquished Dagoth Ur, descends from Red Mountain, and goes to turn in some other quest. He approaches a fairly high-level NPC, talks to them to grab the quest reward, but then...

Ow! My immersion!

What you have encountered is one of the most annoying bugs in Morrowind.
Morrowind dialogue editing presents itself as a list of topics with replies. You have all seen this before, every time you talk to an NPC.

Greetings (the first line of dialogue that you see when talking to an NPC) internally behave exactly the same way, with 10 different "topic" lists, from Greetings 0 to Greetings 9. Whenever you are greeting and NPC, they run down this list from Greeting 0 (related to extremely important quest, like the Vow of Silence) down to Greeting 9 (Location-based) and check each and every "reply" in those to the one that suits your trigger conditions best.

Until you become Nerevarine.

And this is the culprit.

What happens when you advance the main quest by killing Dagoth Ur? These two replies in Greetings 7 do not have any other filter than that very same quest stage, which means they are now triggering every time you speak to an NPC without a proper reply in Greetings 0 to half of Greetings 7.
Quests don't precisely break due to this, but you will never see half of the Greetings 7 replies, and all of Greetings 8 and 9 ever again. For a list of which Greeting topic are supposed to contain, please check our handbook.

While most modders simply do not have enough dialogue in their mod to see this as a problem, province mods like Province Cyrodiil, Skyrim: Home of the Nords, and Tamriel Rebuilt have or will have more dialogue than Morrowind, Tribunal, and Bloodmoon combined. Without a proper fix, we need to put too many of our Greetings in the Greeting 7 list, starving 8 and 9 of content and cluttering it up tremendously. Especially location-based Greetings are taking up a huge amount of space in a Greetings list which was supposed to handle misc achievements.
The alternative to fixing these lines are cluttering up Greetings 7 with more and more locations or accepting that some players will never see these Greetings as they use no fix or a wrong fix. Neither of these are good solutions. The only good solution is a fix, a real fix.

Much better.

As the E-e-e-excuse me reply is straight on top of two replies filtered to the Commoner class and expresses the right sentiment, it seems that these were originally intended to be filtered to the Pauper class. By filtering it correctly, the poorest folk of Tamriel will continue to fawningly stammer over you like the hero you are, while everybody else can move on with their lives and insult your clothing or tell you about the local quest hooks.

What is more important is: who else does anything with these lines?
Aside from the big province mods, it is patch creators and greetings changers that need to work with these lines.
As the for most widely used greetings modifier Morrowind Patch Project (only 1.6.6. was tested) adds the same filter, but also strangely relocates these replies at the very bottom.
The Patch for Purists mod currently implements a different fix, but its creator Half11, is going to change this to using the same filter the province mods will use.

In short: for most users very little will change. For those with an unpatched game (or using an older patch or one of the Nerevarine greetings fixes which did things differently), suddenly old replies will reappear. Modders will be assured that their Greetings in 8 and 9 will actually trigger when they mod for a province mod or assume a reasonably patched game. And finally, for us, it will allow us to make use of two entire Greetings without risking people no longer being able to see anything but excuses.

Another pretty picture, this time from SHotN.

And one from PC. Not pictured: the bugs not occuring because PfP fixed them.