For the greatest part, dating sites aren't doing anything unusual. Sometimes you need to see through their marketing ploys. Sites generally create taxonomies and match users focussing on their answers. In some cases, sites examine the gap between users' responses and their behaviours. For example, you may say that you like a very tall man with dark hair who follows a religion, but mainly click on profiles for stockier non-believers. As such, the algorithm would try to match you according to your behaviour.
However, maybe you're going on all of the profiles and even those that don't meet your preferences, or you’re sitting next to your sister, and she is also after a boyfriend – one who is short and blond. In that case, the algorithm will not work either. It's best to think of dating sites as giant databases for you to search through.
Long profiles generally didn't fare well in my tests. I think that for cerebral women, or women who are quite intellectual, there's a tendency to give a bigger bio. Popular profiles were shorter and intriguing.
Why are Upworthy and Buzzfeed are so popular? It's because they have mastered the art of the "curiosity gap". They provide just enough information to gain interest, which is exactly what you'd do if you met someone in person. This doesn't mean your profile should begin with "9 Out of 10 New Yorkers Are Completely Amazed By This Mind-Blowing Fact" or "You'll Never Believe Who This Person from Somerset Wants to Date …" However, it does mean talking about yourself in roughly 97 fascinating words.