In Skyrim, the player's dialogue is capped to a certain character (typed letter) limit. That's why the player's dialogue responses often sound uninformed, very blunt, bored, not very effusive or detailed.

*Here's an example: Context - Erandur has just finished sending the Skull of Corruption to the depths of Oblivion.

Vanilla Player Response: Are you going to be all right?
Edited Player Response: I hate to leave you in this dark place. Do you think you will fare well?

The difference is that the dialogue option is longer. Now, that particular example isn't actually against the letter limit, so I'll load up Denizens of Hjaalmarch (DoH)--NOT Denizens of Morthal (DoM)--and give you an example of one that probably is. [/spoiler]

*The example that was provided above is NOT part of Denizens; it is from a mod of mine, but it is not a published one.

This is some of Valdimar's new dialogue about the Dawnguard questline in DoH. It takes place in the middle of a deeper conversation, so it is not a starter topic. (You'll see what I mean by that in a bit.)

Uncapped Player Response: You can't keep blaming yourself for what happened to the Vigilants. You honor them best by keeping your focus and staying in the fight.
Letter Limit Player Response: Look, it's over. Stop blaming yourself.

See what I mean?

Uncapped responses shouldn't cause any real problems per say, but when they are the starting topic of a dialogue tree, there is a chance that other dialogue options will not show up on the screen. Usually you can get away with one uncapped starter response, but if there are other uncapped responses (be they from dialogue re-write mods or just other mods that add their own dialogue options to NPCs), then they will war with each other for the right to be seen in the dialogue options sector.

That's why you get a mod like the Minimal Oblivion Dialogue Menu; it can help make all the responses show up.