`cmd > file.txt 2>&1` vs `cmd 2>&1 > file.txt` always tripped me up: the first form is what I usually want (send both to file.txt) but always felt backwards to my brain.
Prompted by Julia, I read up on https://www.gnu.org/software/bash/manual/html_node/Redirections.html and tried to understand why the first incantation sends both outputs to file.txt
Also TIL zsh "MULTIOS" which sends stdout to your pipe even if you've redirected to a file.