Ok, so you complete the Dark Brotherhood questline.

You've killed Empire Titus Mede II - the Emperor responsible for the Empire's handling of the Thalmor war.

Yes, the one and the same Emperor of the Cyrodillic Empire. Yeah, that guy.

And Stormcloak guards walk around saying, "The Emperor of Skyrim is dead. These are dark times."

OK. Emperor of Skyrim???? Who the hell wrote that line?

And since this is obviously supposed to be a reference to Titus Mede, why is a Stormcloak soldier upset about it?

DAH!

/rant lite

there are loads of what guards say threads

At least it's not like what happened right after I killed him. I killed the emperor, swam back to Solitude, and the first guard I met congratulated me for vanquishing a great evil from Skyrim!

Hmmm... Not sure if I see a problem with this. The Stormcloaks are quite aware that the Thalmor are the real enemy. And despite their more immediate civil war with the Empire, they may know the Emperor's death could strengthen the Thalmor's position. Big-picture-wise, it's a bad thing for everybody who doesn't like the Aldmeri Dominion.

Maybe he was respected as a worthy opponent too.

I'm not so sure about that, given that the situation with the Thalmor is largely Mede's fault in the first place. With him dead a ruler can be appointed (I think that's the right term) who actually knows what the hell he's doing, and who might actually act against the Thalmor instead of sitting on his thumbs.

That aside, considering that the Empire and Stormcloaks are on opposite sides of the Civil War, the dialogue should have been written accordingly. After all, for a Stormcloak, the death of the Emperor is a good thing, as it will bring the Imperial Army to a halt while a new leader is chosen, giving the Stormcloaks the opportunity to seize key objectives.

Now if you'd said that a dead Emperor was bad for Skyrim, then I could agree with you, although given the known ineffectiveness of Mede since the WGC even that's debatable. Of course, that assumes that the Thalmor would act immediately upon learning of this, and from all indications they're not really in a position to do so due to lack of sufficient forces, so at least in the short term the Emperor dying might prove no more than a minor inconvenience.

Actually, historically, the Emperor dying on Skyrim soil would be a horrible thing.

These things usually result in entire empires rising up for some serious revenge-minded crusades.

WW1 for example.

That's true, however he doesn't die on Skyrim soil but instead on an Imperial boat. Now, why he goes into hostile territory with a meager guard is another discussion...

That one had me wondering what the devs were smoking. I know TES is fantasy, but I do like to have some plausibility and logic built into the lore and questlines.