This document is my attempt to justify my proposed changes to the font glyphs by adding some more details.
Blender currently ships with four different fonts. Two are fixed width (for text editor and few other places) and two are variable width (used in most places of the interface). For each of these two types there is one small version containing mostly lower Latin characters (and therefore only working well for English) and an optional larger version that contains characters from multiple languages. By default the two minimal fonts are used, but you can enable the use of the larger international fonts by selecting the "Translation" checkbox in Preferences / Interface.
The Keyboard Glyphs
Fonts can contain symbols and we make use of some when indicating some keypresses. Some keys, like "←" are easier to describe with a single symbol, rather than writing a more verbose "left arrow". Some keys, like "⌘" on Mac are more often shown as a symbol than written out as text as "command" (has been called "Apple key", "clover key", etc).
Do we need to show these as symbols? At least sometimes. Many Mac users would prefer nothing but symbols, while many Windows users would prefer nothing text descriptions so we at least have to support the use of symbols, even if their use differs by platform.
Do they have to be shown as font symbols? Yes. Although there are some times when we could have used icons for these, there are many times when these symbols need to used within text content. And in those cases it is important that they be scaled with the text to any size.
Font Type Reconciliation
There are some glyphs that are in the fixed-width versions of the fonts but are not in the variable-width version. The Event Icons (shown in the footer) deal with this by selecting glyphs from one font versus another. But this does not help for other uses. For example, Mac users would like to see "⇧" used to indicate "Shift". Currently we can see this symbol in the footer but cannot see it in the menus for keyboard shortcuts because the symbol is not in the variable-width small font used in the UI by default.
By ensuring these symbols are all in the UI font, not only can we then see them properly in the UI to indicate shortcuts, but it also allows us to simplify the Event Icon code since it no longer has to select from multiple fonts depending on glyph.
International Font Reconciliation
There are some symbols that are in the minimal (English) font that are not in the larger international font, and vice versa. It is very important that the international font be a complete superset of the smaller font. That is required for us to eventually use only the international fonts.
Size and Alignment
Our four fonts are all meta-fonts, containing characters from a number of different fonts. Over time each has gained new glyphs as they were needed, from a variety of donor fonts. Because of this the keyboard symbols we use do not share common sizes or alignment. Had they all be taken from the same font then each would work together harmoniously, with the same width, bearings, and vertical alignment.
By making these symbols share common sizes and alignment they can be placed by each other and still be readable. So if we need to use "⇧⌘" together we want them to be harmonious.
And by making these gylphs similar size and alignment it also means we can further simplify the code in Event Icons that has to currently deal with per-character adjustments.
Once these glyph changes are accepted we can then use these characters where we want. For Macs this is important for shortcuts, but it also comes in handy for Windows users too. Although Windows users prefer text over symbols for things like "Ctrl" and "Alt", it would still be nice to use symbols for "Windows key" and "Menu key" since those two are never shown as text on keyboards.
Once we are able to swap out our minimal font for the international version without errors, we can consider making the international font the only fonts used. And at that point we can use a subset of the smaller font as a fallback font. That way if a user replaces the main UI font with something else they can still see these characters even if that font does not contain them.