Why incomplete subscript/superscript alphabet ?

[Jukka K. Korpela]

30.9.2016, 18:19, Philippe Verdy wrote:

> Note also that many tools generating documentation from source code
> allow you to insert HTML comments, so you could as well use <sub></sub>,

Yes, but there’s a serious typographic pitfall with this, as well as 
with using e.g. subscript or superscript formatting in a word processor. 
The problem is that the rendering is almost always simplistic: letters 
(or other characters) of the current font are used in reduced size and 
in lowered or raised position. The result is that the glyphs have 
reduced stroke width too, and the position change very often causes line 
spacing to be uneven.

The typographically correct implementation of such formatting or markup 
would use subscript or superscript glyphs from the font, designed by the 
font creator to match the style of the font. This is more difficult than 
the simplistic approach, and of course it is possible only when using a 
font that contains such glyphs.

Using HTML, for example, the way to achieve that at present would be to 
use markup like <span class="sub">...</span> (to avoid the problems 
caused by the default formatting of <sub> and <sup>) and to use a CSS 
style sheet that sets font-family suitably and uses OpenType font 
feature settings to select subscript or superscript glyphs. In practice, 
you would need to use @font-face to embed a suitable OpenType font. So 
it’s doable, but not trivial like just slapping <sub> and </sub> around 
some text.

A practical conclusion is that if you need only e.g. 2 and 3 as 
superscripts (a rather general situation in general texts, where you 
just need m² or m³), it is much simpler to use the relevant Unicode 
superscript characters (instead of e.g. m<sup>2</sup>). This means using 
typographer-designer superscript glyphs in a simple and reliable way.

Yucca