It's like asking for "actual evidence" about what color you should wear to dinner. It depends on the context and setting, and current social attitudes and your

It's like asking for "actual evidence" about what color you should wear to dinner. It depends on the context and setting, and current social attitudes and your positioning relative to them, and your own sense of what looks good based on those elements. Unless you go out of your way to fuck it up most text you put on the web will be legible. And no matter what someone will say it's illegible to them and just raw unstyled html defaults are the most legible. Or the raw html defaults are unreadable and anything else is an improvement. etc etc. It's got technical foundations so it's easy to pretend otherwise but it's still aesthetic choices. Math won't really help you here. In fact building fonts off of "mathematically ideal proportions" was a popular thing for a while and is now mostly considered a regrettable dead-end. The things that came out of it don't look better and aren't overall more readable.