One unfortunate problem is that nobody bothered setting the measure for legibility. On my display the text block is far far too wide. Cf. https://en.wikipedia.org/wiki/Line_length (while we're talking about typography, the fonts for body copy and code are mismatched in size in a distracting way)
As far as formulas/notation is concerned, the notation used in this paper is targeted only at experts in theoretical computer science, approximately the level of advanced grad students or above, who also happen to be pretty familiar with Rust and C++. The gimmicky popups are probably not meaningfully helpful for such an audience, and in my opinion don't really make the notation any more accessible to people without the extremely steep prerequisite expertise (e.g. I don't think this paper is going to be at all accessible to the vast majority of working programmers or computer science undergraduate students).
If you really want to make the paper more accessible, it would be better to focus on reducing the reliance on formulas, reducing the amount of jargon involved, and explaining the concepts and techniques using plain English targeted at a broader audience, rather than trying to add extra colors, click targets, or popups. (A research paper may alternately want to just target experts; that can also be fine. Even for experts this paper is pretty dense though.)
