This barely matters at all; context will tell you what symbol is being used, just like it does in prose, and most material is typeset.
It really is a very bad idea to use lowercase Ls, though.
Unfortunately after the invention of printing there has been a bad fashion in serif typefaces that made lowercase "l' too similar with other letters, by replacing the traditional hook with a serif identical to the serifs of all letters that end on the baseline, so that the only difference from uppercase "I" remained in a triangular left serif added to the upper end.
Even worse, in the 19th century, after sans-serif typefaces became popular, most of them have simplified lowercase "l" even more, making it almost identical with uppercase "I".
Nevertheless, while many of the typefaces used today follow the bad styles of serif or sans-serif designs with hard to distinguish lowercase "l", there exists a decent number of typefaces which have returned to the original form of lowercase "l", with a right hook at the lower end, which is easy to differentiate from any other letters. I am using almost only this kind of typefaces. Examples are Palatino Sans and FF Meta, but there are many others. Also all recent monospace typefaces intended for programming have such lowerspace "l" (being a narrow letter, in monospace typefaces lowercase "l" also has a left slab serif at the upper end, to expand its width).
In handwriting, the best solution for lowercase "l" is not to make it cursive like suggested in the parent article, but to make it with a low right hook, like in its original ancient form.
It might help a little. "Easily distinguishable" is dramatically overselling things.
https://upload.wikimedia.org/wikipedia/commons/b/bd/Minuscul...
I, capital and lowercase, also has a serif hooking to the right at the bottom of the stroke. Look at the first line beginning with a big red I.
It says "Iterum autem pilatus locutus ẽ. ad illos volens".
The line above it says "Et homicidium missus In carcerem;".
How much difference do you see between the capital I in "In carcerem" and the lowercase L in "pilatus"?
It's easy to distinguish lowercase L from lowercase i because L is taller. Capital I is only slightly different.
(I should note that wikipedia's page on Carolingian minuscule also includes an image of a page of written Slovene. I couldn't really use that as an example, because without any knowledge of Slovene I can't reliably identify the letters. But I think that goes to show that the alphabet by itself doesn't reach the level of perfect unambiguity.)
I'm interested to see that all Ses look the same. At some point we got word-final "s", but this was clearly not that point.
The serif at the lower end of capital "I" is bilateral symmetrical, besides having a flat termination, so it looks very different from the asymmetric and curved right hook on lowercase "l".
Also in my handwriting, I write lowercase "l" with a right hook and uppercase "I" with serifs, making them impossible to confuse.
No, look at the capital "I" that I indicated in my comment. It has neither of those qualities.
Despite this defect of this particular letter, which is not a frequently seen defect, I still cannot see how the right serif could be confused with a right hook. The letters would have to be much more degraded for the difference between an orthogonal serif and a curved hook to become invisible.
I agree that the differences between the 6 narrow alphanumeric characters "1IJijl" are small so they are more likely to disappear when the letters are partially erased, but when the letters are intact and they have been written with the right distinct shapes they can still be distinguished easily, in contrast with some typefaces (usually sans-serif typefaces) where they are intentionally made more similar than they were traditionally, which has been a very bad idea, so such typefaces (e.g. Helvetica or Arial) should be avoided.
https://en.wikipedia.org/wiki/Minim_(palaeography)
I guess blackletter script was an obstacle to mathematics (and reading).