Unicode Explained

Characters with <compat> mapping in general

The report vaguely describes that “the <compat> label was given to a set of com-

patibility characters whose further classification was not settled at the time the

standard was created.” This seems to ignore the possibility of simply replacing the

character with its compatibility mapping—e.g., writing ℅ as “c/o.” Perhaps the

idea is to say that if the formatting or the special meaning is to be preserved, there

is usually no other way than to retain the character. In some situations, such as

vertical layout, it is necessary to keep the symbol as single character, and vertical

layout is one of the reasons why the characters have been used in the first place.

Besides, due to relatively poor support in fonts, most characters in this category

are rarely used for purely typographic reasons. Therefore, it might be safest to

assume, at least in automatic conversions, that if these characters appear, there is

a particular reason for that, so they should be retained as such. On the other hand,

if you know that, say, the character Roman numeral seven Ⅶ (U+2166) has been

used just for typography or by mistake, it’s hard to see why you could not replace

it with the three-character string “VII,” optionally with some styling.

Fixed-width spaces

The report recommends that these characters be retained. However, as described

in Chapter 8, most fixed-width spaces work ...