unicode-math should not be the default

[FelixBenning]

I was using quarto to generate latex/pdf and html output and the blackboard $\mathbb R$ looked much worse than usual in the pdf output. This was not the case when using the pdflatex engine so I tried to figure out why this is the case. The reason is hidden in the font.latex template partial

pandoc/data/templates/fonts.latex

Lines 6 to 18 in 8d93cd7

	\else % if luatex or xetex
	$if(mathspec)$
	\ifXeTeX
	\usepackage{mathspec} % this also loads fontspec
	\else
	\usepackage{unicode-math} % this also loads fontspec
	\fi
	$else$
	\usepackage{unicode-math} % this also loads fontspec
	$endif$
	\defaultfontfeatures{Scale=MatchLowercase}$-- must come before Beamer theme
	\defaultfontfeatures[\rmfamily]{Ligatures=TeX,Scale=1}
	\fi

unicode-math is a package that allows the usage of unicode symbols in the input but deteriorates the visual quality of the output. There are a bunch of stackexchange questions related to this, e.g.

• unicode-math but ordinary blackboard bold
• How can I get Latin Modern/Computer Modern serif double-struck/blackboard-bold characters which copy/paste as unicode when using unicode-math?
• How do I get normal \mapsto and \colon symbols when using unicode-math?
• XeLaTeX, Latin Modern, \mathbb and \mathcal

Since it is difficult to type these symbols on a keyboard and people coming from a LaTeX background are used to the macros it is probably fair to say that there is only going to be a small set of people that actually use the features of the unicode-math package, but its inclusion significantly deteriorates the visual quality of the pdf output.

Given the lack of pushback on the statment "this looks so much worse than the amsmath blackboard letters", e.g. in here

• https://www.reddit.com/r/LaTeX/comments/1dvkxuj/why_does_my_mathbb_r_look_so_bad/

I would also say that this subjective opinion is very widespread. Moreover in the only discussion on this topic (#10587) unicode-math was rejected

TL;DR unicode-math should not be loaded by default.

[FelixBenning]

An alternative may be the use of the "New Computer Modern" font. E.g. with

\usepackage[default]{fontsetup}

although that still changes the spacing of the norm $\|$ symbols

[jgm]

@wilx do you want to comment on this?

I would recommend experimenting with different settings for mathfont (in metadata or variable).
Most likely you are using a font that doesn't have good glyphs for these characters, but that's just a matter of font choice.

[jgm]

For reference, here is what $\mathbb R$ looks like with pandoc/pdflatex:

and with pandoc/lualatex:

[jgm]

but with -Vmathfont="Garamond Math" for example:

and with "TeX Gyre Schola Math":

[wilx]

It seems to me that one of your links explains this: https://tex.stackexchange.com/a/577603. The default font is Latin Modern and its Math font. You don't seem to like the Latin Modern Math font. But for some other people it is a pair designed together.

I suggest you just change the math font to the one that you like. Look at the List of symbols defined by the package document in unicode-math to see which one seems the best for you.