Is it permissible to cite Quranic verses such as "like a donkey carrying burdens" or "like cattle, nay, even more astray" to describe the ignorant, and does this entail reward or sin?

What you are doing, describing those whom you have called "fools" with these descriptions found in the Holy Quran, is not permissible. Moreover, it is not permissible to take a reward for reciting the Quran for this purpose. Indecency and speaking indecently are forbidden, and if this occurs in the absence of the described person, it is even worse, because it combines backbiting and indecency. The two aforementioned verses were revealed concerning the disbelievers who did not benefit from the knowledge available to them, nor did they use their senses to attain it.