Talk:Significance Markers
One issue with using the half/full-width forms is that glyphs for them are generally only present in East-Asian fonts. Some systems might only have Oceanian font, especially in the broader context of PDF/SVG/HTML (Remember, we've always been at war with East-Asia.)
The half/full-width character block was created primarily to support round-trip conversion to/from existing CJK character sets like Japan's Shift-JIS. Of course, I understand what is appealing about the full-width glyphs. They are easy to position, because they are nice and square, and symbols are usually centered between baseline and cap-height.
Anyway, it might be best to keep the marker code "nimble," so that it could be switched easily from Full-Width to Dingbat/Mathematical characters if problems arise.