Some misunderstood or unknown tricks (XIII) (LaTeX)

We will here again consider many tips and tricks. This time, they will mostly come from Glad Deschrijver, TeX Tricks, 2011. (http://users.ugent.be/~gdschrij/LaTeX/textricks.html.) Tricks: vertically aligned itemize environments, allowing linebreaks after comma in math mode, writing under and over elements, and using stacks, footnotes with a new number at each section, footnotes in tabular, splitting algorithm environments on multiple pages, let " produce opening/closing quotation marks, indenting some text but not the first line, using diagonal dots positioned according to the opposite diagonal, using a centered verbatim environment, drawing a table with dashed lines, shaded cells and arrows pointing at a row and a column, correct spacing around square brackets (used for sets) in math mode.