> Prefer words to icons. Use only icons that are universally understood.
Underrated. Except for dyslexic people, and the most obvious icon forms, I am pretty sure most people are just better and faster at recognising single words at a glance than icons.
...except for HN "unvote"/"undown" feedback which is especially unfortunate due to the shared prefix. Every time I upvote something I squint at the unvote/undown to make sure I didn't misclick.
I am pretty sure icons are easier and faster to recognize, except when you make them (too) small. In particular, they probably are easier in the long run, as long as they don't change position. But in a context where things change or you need a lot of buttons, words probably win.