How to reduce white space inside “𝑌.” automatically?

Question

Feeding

\documentclass{article}
\pagestyle{empty}
%\usepackage[slantedGreek,subscriptcorrection]{newtx}% this is what I use with many of other packages in a non-minimal example.
%% Text skips with glue being half of the value of the argument (cf. http://tex.stackexchange.com/q/657443, http://tex.stackexchange.com/a/657448, and http://tex.stackexchange.com/a/672701):
\newcommand{\flexibleHSkip}[1]{%
  \hskip#1
  plus.5\dimexpr\ifdim #1<0pt -\fi#1\relax
  minus.5\dimexpr\ifdim #1<0pt -\fi#1\relax
  \relax
}
\begin{document}\noindent
Consider the set \(Y\). Let \ldots\\
Consider the set \(Y\)\flexibleHSkip{-.1em}. \flexibleHSkip{.1em}Let \ldots\\
Consider the set \(Y\)\flexibleHSkip{-.1em}.\flexibleHSkip{.1em} Let \ldots\\
Consider the set \(Y\), and let \ldots\\
Consider the set \(Y\)\flexibleHSkip{-.1em}, \flexibleHSkip{.1em}and let \ldots\\
Consider the set \(Y\)\flexibleHSkip{-.1em},\flexibleHSkip{.1em} and let \ldots
\end{document}

to pdflatex yields

with standard fonts (Computer Modern) and

with NewTX. The versions with the reduced space between 𝑌 and the punctuation mark seem better to me (and, hopefully, to you). The macro \flexibleHSkip{…} allows for stretching and shrinking to allow for prettier lines and paragraphs; if you don't care, you can use simple \hskip-.1em and \hskip.1em instead, for instance.

1. If we manually reduce white space before punctuation and add white space after punctuation, which version is correct™, i.e., causes less issues (I might imagine that line breaking could be hypothetically affected): \flexibleHSkip{-.1em}PunctuationSymbol\flexibleHSkip{.1em} or \flexibleHSkip{-.1em}PunctuationSymbol \flexibleHSkip{.1em}. In other words, what should be the order of the regular space symbol and \flexibleHSkip{.1em} after the punctuation mark?

2. How to get better spacing between “𝑌” and [“.” or “,”] automatically, without manual space deletions and insertions in the source document?

Answer 1

I would simply pull the . in to the math, it will be taken from the mathrm font anyway and allows the font-specified kerns to take effect.

\documentclass{article}

\begin{document}

$Y$. ABC

$Y.$ ABC


\end{document}