I have difficulty differentiating "l" and "1" when reading source code, i.e. monospace serif types. I am able to tell which is which when looking more closely, but regardless of my eyesight, this requires additional concentration.
From my tests, this stems from the arrow head of the "l", which in combination with a wide base looks very similar to a classic "1" (e.g. in Courier Prime).
Notably, this confusion is greatly reduced when using either no arrow head (which looks a bit strange!), or a half width base (Fira Mono), or both (Monoid).
However, looking at http://www.s9w.io/font_compare/, it appears the problematic combination is easily prevalent.
Why is that? Should we not work more to remove this issue? Or is it just me having trouble?
I do understand that sans serif, the letters will look similar - but I'd hope that monospace serif would fix it, by using all the additional space available. In particular since some of the offending fonts were especially created for use in programming.
Edit: It should be noted that the problematic shape (the lower case L of e.g. Courier Prime) is commonly used to denote a '1' in other fonts (though often in reduced height, e.g. in FF Seria Sans). This surely contributes to my mind reading it as a '1'.