Mathematical notation is not readable, no. It requires extensive training to be able to understand it, and even experts will take quite a while to comprehend a document they are not already mostly familiar with. It is not like you cross some threshold and immediately become able to understand all mathematical notation with equal ease. There's plenty of evidence for this; recently we had this quote about the ABC theorem: "It can require a huge investment of time to understand a long and sophisticated proof, so the willingness by others to do this rests not only on the importance of the announcement but also on the track record of the authors" (http://www.nature.com/news/proof-claimed-for-deep-connection...)
> even experts will take quite a while to comprehend a document they are not already mostly familiar with
Experts don't take time to read notations. They take time to understand the full scope of consequences embedded in a line composed of such a condensed and readable notation, within the frame of an otherwise complex proof.
> Mathematical notation is not readable, no.
I beg to differ. You mention the recent possible proof of the ABC conjecture, and I happened to browse through various materials on the subject. While I am far from being able to understand the crux of the proof, I can perfectly read the various components of it. In fact the notation system is so readable it actually helps tremendously in grasping concepts previously unknown to me.
Other examples that highlight how understanding of mathematical research involves much more than just reading: https://docs.google.com/viewer?a=v&q=cache:5NM3XjxAWfUJ:... http://math.stackexchange.com/questions/13460/how-to-read-a-...