Just wanted to say I'm really enjoying this discussion. For what it's worth, 
I see one detail from the sketch that might argue against Twain as the 
author: his use of the phrase "an humble citizen."

Somewhere among his writings he makes the point that the British use "an" in 
front of words like "humble" with what you might call a hard H (indicating 
that at one time they dropped the H, Cockney-style), but Americans do not. 
And just off the top of my head, I can't recall a case where he used "an" 
that way.

Of course, it's possible that a typesetter changed "a" to "an" -- or that 
Twain actually did use "an" in some cases that I'm forgetting. But I thought 
I'd mention it anyway.

-- Bob G.