I thought that katanas were forged by the Blades, fashioned after the weapons the Akaviri use.

Blades aren't the only ones to use katanas. The Teaseci had a profound influence on Cyrodiil, especially in the Nibian where they were welcomed into their culture. 1st PGE talks about houseguards wielding massive katanas at intersections and cross ways for instance.

Katanas aren't exclusive to the blades, though modern Tamriellic katanas are an appropriation of Akaviri weapon designs. Cyrodiil especially is known for appropriating and venerating aspects of Akaviri culture. It's not really surprising that a the Ancestor Moth cult, with it's close ties to the Emperor, would also be influenced by Akavir.

I'm continually amazed by the knowledge of the posters in this forum. Thanks!

I assume the Blade's armor is also more Tamrielic than Akiviri. Since the Akiviri did not wear armor (or generally had no use for it), I guess we have to assume that the armor is simply Akiviri in fashion and not necessarily form or function?

http://images3.wikia.nocookie.net/__cb57524/elderscrolls/images/9/92/AkaviriCommanderMishaxhi.jpg seems to disagree with you.

Akaviri ghost was written off as techincal limitation due to inability to properly display the Taeseci (via former dev comment).

source?

It didn't survive the forum purge. The comment was made by Michael Kirkbride, the creator of the Taeseci a few years ago around the time of Oblivion.

http://www.imperial-library.info/content/forum-archives-michael-kirkbride

To further, he assured us that the Taeseci were "immortal.vampire.snakemen"

Then I retract my statement and apologise. I didn't know. Thanks for the correction, and I sure would love to see me some Tsaesci. I actually thought that these ghosts were the humans of Akavir from before they were eaten, but I assume from your comment and that they actively explained that it wasn't, that it must in fact have been a Tsaesci. Such a shame! I would have loved to see a snakeman ghost and tell that Countess Narina about it all.

Cource, this all has been challenged as of late with the Alduin's wall and Beth may have decided to adopt a more human visage given new developments. Alot of people around here have more so embrased the new idea/change. I'd say make up your mind for yourself on the matter, as of now, its still somewhat of a mystery.

I like the idea of the snakemen to do a reverse dracochrysalis, or rather a homochrysalis (no pun here) in the sense that they long for becoming human. Possibly through eating them.