[johndough]

Two more heuristics:

1. The figures are not vectorized (text in figures can not be selected). All it takes is to replace "png" in `plt.savefig("figure.png")` with "pdf", so this is a very easy fix. Yet the author did not bother, which shows that he either did not care or did not know.

2. The equations lack punctuation.

Of course you can still write insightful papers with low quality figures and unusual punctuation. This is just a heuristic after all.