This is incredibly frustrating because you only find this out after having written a lengthy review already. There is no way to know before trying to submit a review that is rejected. So what this means is that people spend a lot of time writing extensive reviews, only to find out that they wasted their time because they can't submit them.
1500 characters is the length of an extensive summary, not a review that actually tells you
why something ends up being a good or a bad thing. There is no room to elaborate. And that, I think, is exactly what a review should be about. Anyone can give a rating, but that usually doesn't meany anything to anybody else. What a review must do is be descriptive, so that people can decide whether that suits their tastes or not.
I don't think this helps quality at all. None of the poor two-line reviews get rejected. The long reviews, into which people usually put a lot of thought, are the ones that are being kept out. We already have a voting system for quality control. If a long review is just a pointless rant, it will get voted down, fall farther and farther back in pages, and be out of sight. The good reviews, long or short, get upvoted and appear up front. I don't see why any other measure would be needed.
And for crying out loud, you can set a hard limit on the content length of an HTML text box, or even add a JavaScript character countdown, so that people who are in the process of writing an in-depth review at least
know that they won't be able to finish it. YouTube's comment limit is 500 characters, and even they have the courtesy to tell you when you're running out. The current situation is really as unsatisfactory as can be.
The above text, not including this note, has 1692 characters.
Shadowcat: I don't believe I shall ever write another review here again unless I hear that (a) you have increased the character limit, (b) you actually tell the user what the limit is (and ideally how far over it they are), and (c) you allow at least some short-term editing of reviews, so that simple typos and errors can be corrected.
I agree with all of the above points. Make it happen!