So I'm going to disagree with all my learned colleagues downthread and suggest that the humour - more precisely, the way the humour was executed - clashed with the tone of the rest of the work. It's not that you can't make something funny and very serious as well: see Sir Terry Pratchett. What didn't work for me here was that there were two different tones being taken. The work opens in a relatively serious voice. The introduction of the monks breaks that voice sharply. The monks are exaggerations - overdrawn and ridiculous to the point of cartoonishness. Meanwhile the other characters are not. Both Choth and the narrator are more down-to-earth, realistically drawn characters. There's also nothing exaggerated or larger than life about the Copperclaw kingdom or the people of Cornwell (and do I understand there's a word count limit in play here). So the rat monks are silly bordering on slapstick, but there's not even a hint of the same comic tone in the other characters, the broader outlines of the world, or any of the prose unrelated to the monks. That's why I found the humour jarring.
Phew! That was a lot of words. I hope you understand what I'm trying to express here. And for clarity, I *liked* the humour. It was funny and well-done! If the rest of the work had struck a more lighthearted, exaggerated tone it would have landed perfectly for me.
On the whole, I did like the work. Everything flowed along nicely, the prose was sharp and enjoyable, and the worldbuilding was solid. I enjoyed the use of moons rather than years as a measurement of age as a way of illustrating the different pace of life among the much shorter-lived ratmen. I really liked that the major conflict was between ratmen factions - there's a lot of lip service paid in legacy to the rats being riven with inner conflict but they always seemed to unite without problems when it came to waging war on the "good" races, and I liked that you used real conflict between ratmen factions as a plot driver here.