Many people select fonts where there isn't ambiguity between similar characters like o/O/0 and I/l/1. Reading the home page for the font [ https://concoursefont.com/ ] gives me a headache personally. The lowercase 't' and 'f' fight one another. The 'f' with its flowing curve and the 't' in its rigid straightness makes the text fail to flow well.

My favorite font is guilty of having ambiguous characters as well - and while I'm not personally very bothered by it - I can understand and empathize with the annoyance other people have towards issues like this.

I use Stylus to inject my own stylesheets and force every website to use my chosen fonts - their design be damned. But I also eventually write my own CSS for the site myself if I use it frequently so my opinion is likely invalid as 99.9999999% of users would never do that.

As an aside: I don't use Concourse as a body font; it's not something that strikes me as particularly suitable for long stretches of text. But I think it's fine in headlines. It also has multiple letter variations you can use, and my web site uses the "British" stylistic set, which has a different "f" and "t" (and "l" and a few other characters) from the default used on most of its site.