[durumu]

IMO using a lowercase l as a numeric variable is cursed. It is way too easy to read it as 1 in many monospace fonts.

[sitkack]

I totally agree. Maybe a font with boxes around the numbers? Or some other way to disambiguate them.

[rozab]

Perhaps some sort of system could be implemented to cause the teleprinter to use a different variety of ink, depending on the nature and syntactic context of the symbol

[sitkack]

I like this, for bold it could backup and hit that char again.

[gsck]

Or just get a font that draws the i with a line and a dot correctly, and a 1 with the horizontal line at the bottom and the half width line at an angle at the top.

You are using a bad font.