Arnis: "The turning off of properties using the <Default ¶ Font> tag is probably a habit that goes back to some buggy behaviour in very early editions of FM where occasionally a specified character format would spill out of an x-ref (or was it a variable?). FWIW, it's easier and more convenient to use </> instead."
Is </> documented anywhere?
And is it identically equal to <Default ¶ Font>?
It would be nice to have a Variable construct that just means
</ChFmt> "terminate the most recent markup", rather than
<Default ¶ Font> "reset defaults for the remainder of the string to whatever para/char formats happen to be in effect."
For example, if doing an arbitrary 11/17 fraction in the pre-Unicode way as
<Superscript>11<Default ¶ Font><Symbol>\xa4<Default ¶ Font><Subscript>17
with a font override applied to the para, the denominator reverts to the Paragraph format and loses the override (yet another reason to avoid overrides, to be sure).
It is possible to create bookend Character Formats for some things, for example </Superscript> which is identical to <Superscript> except for the Superscript attribute, which is off for the </ version.
But it doesn't seem possible to do the same for a font tag like <Symbol></Symbol>. There is no undo for the font Family:, only an "As-Is" which unsurprisingly appears to do nothing.
This specific example is done much more elegantly with Unicode these days (often entirely without Character Formats), but there are doubtless other cases where a </ChFmt> tag would be useful.