That's not a request for clemency. It's the arc of the English word, loosed like an arrow.

he is asking for clemency without requesting it - i mean that's the point of quoting Matthew at the end of the letter. But I agree, this is an amazing piece of language...

That's a good point: the verse at the end seems to be a request for mercy. Those who show mercy are shown such in return.

But kings are not in need of mercy, being sovereign. So it seems more of a "You're a human being too, dude. And you'll get yours."

All of his references in the letter support the latter.

Check out the verses that sandwich Matthew 5:7:

Blessed are they which do hunger and thirst after righteousness: for they shall be filled.

And

Blessed are the pure in heart: for they shall see God.

Heartbreakingly, this could be interpreted as Assange is still convinced of his purpose, and that his suffering is... nearly over.