So, after having access to the CK would it be possible to reach a consensus on the Ebony Blade. Are their 'unique' characteristics a bug or intentional?

At first I assumed that the mismatch between 1H and 2H skill was intentional, a way of making this artifact unique.

But after having anolyzed the script in the CK, I weighted these facts:

-Not only the blade uses the 1H perk tree but the speed and sounds are from a 1H weapon as well. In other words, it has the same DPS potential and behavior of a one hand longsword with a base damage of 11 (like a... Katana!)

-All the other katanas look-alike are 1H weapons. The ebony blade was a one hand weapon in the past Elder Scrolls games.

-The ebony blade is only treated as a two handed sword for the animation and base damage, which can easily be explained by a developer mistreating one single variable and having the rest correctly assigned to one hand weapons.

What do you think?

There are a few weapons that are 1 handed skill but two handed in use, the Headman's Axe for example.
They can be handy to boost up you Two handed skill, which they increase during use, if you have maxxed your 1 Handed out first.
The Ebony Blade is a larger weapon that the other Katanas too, suits the Two Handed use I think.

I would agree with you were not for its template which is the same of a 1H sword including speed of swing and impact effects. One way or the other, I think someone at Bethesda messed up a few things with this weapon.

Well, it's scripted to do those things, so I reckon it may have been intentional.