This is really great, Vitaliy! Seeing the way the representation changes as the window moves through time is very interesting. It made me think of another representation -- different but quite similar.

Picture a network map which includes all the words ever used, with their spacial proximities determined by how close in time their utterances were, on average, to each other. But now represent their usage densities, within each time window, as a magnitude, and represent that as something like a color or a value (like saturation or value in the colorimetric sense), or even a height of the characters, as in a 3D histogram. Now we see a connectedness representation, as well as a time evolution. It would be interesting to follow a political campaign, or a debate, or even the conversation at a lunch table, as the discussion went from subject to subject.

Thank you for your suggestions. Indeed max number of words could be an interesting option to take advantage of. I already played with various DisplayDurations and slowing it down makes it more boring to my taste. I was thinking that maybe there are method of packing words that allows to keep same words mostly at the same positions. Most of the jumping is not due to disappearance of words but their sudden relocation. But this sounds like a tough problem.