Fonts and Unicode conformance (was Re: Use of tag ,,,)

[James Kass]

On 2024-05-07 2:23 AM, Erik Carvalhal Miller via Unicode wrote:
>  ⁠•⁠ ⁠⟨☄^!313125⟩ is valid Unicode, such as it is.  If in normal 
> reading mode itʼs meant to be replaced by a different comet or an 
> aardvark or a Klingon symbol for empire or anything other than a 
> representation of the characters ⁠⟨☄^!313125⟩, then the intended 
> interpretation is not valid as Unicode plain text, though it may be 
> perfectly valid markup of some sort or another beyond Unicodeʼs 
> concern.  If the idea is for a font to make one of those 
> substitutions, then such a font is not Unicode‐conformant.

TTF/OTF fonts are essentially programs.

Years ago, IIRC, John Hudson postulated on an OpenType forum that an 
OpenType font could be designed to substitute innocuous words for swear 
words.  So, for example, if a dog lover developed a font that would 
replace the string "cat " with the string "dog " in the display, would 
that be considered non-conformant?  (Keeping in mind that the font 
display doesn't alter the underlying encoded text and cannot affect 
interchange and storage.)

Or suppose a font developer named Zebediah Waldo Jablonsky set up an 
OpenType font to display a monogram any time his initials appeared in 
all-caps.  Or if a business set up an OpenType font to display its logo 
whenever a string like COMET plus CIRCUMFLEX appeared in the text.  
Would either of those fonts be viewed as non-conformant?

An OpenType font could theoretically be set up to display an aardvark 
glyph for any text string, even for the string <img src="aardvark.jpg"> 
.  Why would a browser program displaying an image for that string be 
conformant, yet a font program doing the same thing be non-conformant?  
(I'm not saying it wouldn't be silly to do so.)