Here's a simple reason
why Moodle should adopt jQuery. According to the linked report, 60.4% of web sites use jQuery and the next highest total is none at 35.9%. Of the other proposed libraries that I remember being suggested, AngularJS is at 0.1% and EmberJS doesn't even rate.
Personally, I think there'd have to be some very persuasive arguments to convince me that going with jQuery is not the best short and long term decision to make right now. I'm prepared to listen to them, but I haven't seen anything that convinces me that jQuery would be a bad choice in this thread, yet. Furthermore, to me the suggestion that we should develop a Moodle specific javscript library instead of using jQuery (or something else) is a non-starter. Even though I've re-invented the wheel many times before, I am generally of the opinion that it is not a productive use of time and energy. That's particularly true if we're going to make a wheel that only fits on our own car, because more often than not when we're done we find that our new square shaped wheels don't work quite as well as we expected them to, and nobody has the the time to sand all the corners down.
Note: Some people have mentioned that there are some bad jQuery plugins among the 2576 plugins in jQuery's official repository and I'm sure they're correct, but I also know there are also some bad plugins among the 899 plugins in Moodle's official registery.