> Short sentences and clear points are more persuasive even if they're nonsense.

What you're describing is propaganda -- an emotional appeal that solicits mindless reaction. That's the basest form of communication -- hardly something to espouse as the paradigm for a good essay.

As Graham points out, the best essays often are not intended to persuade as much as inform. The essentials of writing that's useful to the reader are facts and logic, leading intuitively to a conclusion that is meaningful and important to the audience. HOW you achieve these ends matters less, be they short sentences or emotional appeals.

But illogic has no place in an informative essay. That's the bailiwick of provocateurs, politicians, and propaganda.

When you get to the root of it, there's not much to differentiate between something written to inform versus something written to persuade.

Is there not? I think a big part of the difference might be how defensive one is against a hostile audience. For example, let’s consider that we’re writing about something like the Monty Hall problem. A piece of writing that explains and informs the reader about the Monty Hall problem will describe and work through all of the counter-intuitive logic involved, but it will do so from a position of (a) absolute certainty about the conclusion and (b) a good-faith assumption that disagreeing with that conclusion is due to an innocent mistake in reasoning, which the writer will want to anticipate and patiently address. And this is probably the right approach for the Monty Hall problem, but most of the time you’re writing persuasively, projecting absolute certainty that you are right and anyone who disagrees with you is confused or mistaken isn’t always the best decision, especially when it’s a disagreement over subjective preferences and value judgments. If I was writing an endorsement of a political candidate, I would approach that much differently than I would approach an explanation of the Monty Hall problem. In both cases you do similar things (in terms of presenting clear and explicit reasoning) but there are more differences than similarities.

> The longer your sentences, the more you'll filter out readers with short attentions spans and limited literacy.

And readers who have not yet been persuaded that your writing is worth their time. If long sentences are essential to a point you're making in a persuasive essay for a non-captive audience, use inverted pyramid style and push the long sentences down.