Some users are looking for the TT font to be mono-spaced.
Some users are looking for the zero character have a slash in it (an option per the spec). Some feel this might look too busy on a drawing. Perhaps the notes could have this, but not the dimensions? While drawing lettering is specified to be all capitals except as required, some users want the Upper Case "I" [I] different from the Lower Case "l" [l] (for those rare cases), but serifs are getting the objection.
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I know it's not a TT font, but FWIW, I posted a variation of the PTC standard font called "Font" with the modifications Lance describes to the PTC user portal section some months ago (and also a strikethrough version). Ironically, I hated that aspect of the sans serif font on pro/e drawings, but everywhere else, I despise serifed fonts (you may note that this note email is not written in one).