Some symbols from the Geometric Shape and Miscellaneous blocks have the same weight in all typefaces (Sans or Mono). This is not very useful to have the exact same complex glyphs in many fonts. Sans Bold should have symbols with bolder outlines, they should look darker when possible. This is also taking a lot of unnecessary space. If the user is not supposed to use Oblique symbols, then the symbols should not be present in the Oblique font.
Not so. The size of the font data is not critical on modern PCs. What is critical is, if the Bold or italic style doesn't contain the symbol glyphs, Windows will simulate italics and/or bold, distorting the glyph form its intended design. Worse still, if output to PDF, all Faux Bold and Faux Italics glyphs will be converted to curves, resulting in a huge increase in the size of the PDF. In an ideal world, the users would not apply bold or italics to symbols that do not require it, such as Geometric shapes, but they may use symbols within bold or italic text and will never even consider changing that glyph back to regular. Therefore, all four typestyles should contain copies of all the symbols, and the character advance width should not change, though symbols in italic glyphs benefit from being offset to the right instead of being centred. Many symbols are monospaced, but some require a wider (∞) or narrower (∫) advance width. In my fonts, I added some alternate glyphs as Easter Eggs on bold, italic, and bold italic typestyles among the symbols, but it is too much work to design bold or italic versions of each glyph, especially as in most cases, such designs would be inappropriate. Though one might design a bold Lozenge (\u25CA), if one designed a bold black small square (\u25AA) it would be similar to black medium small square (\u25FE). Possibly there is a flag somewhere that tells Windows not to embolden Unicode symbols or try to make an italic, but I haven't found it yet.
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.