[Tex/LaTex] Has \textsubscript become a standard LaTeX command

subscripts

TeX Live comes with a helpful fragment package, subscript, the copyright notice of which runs as follows:

% Copyright 1999 Robin Fairbairns
%
% this fragment is distributed under the conditions of the LaTeX
% Project Public Licence -- see lppl.txt in the LaTeX distribution
%
% this fragment provides a command \textsubscript, which is
% shamelessly copied from the command \textsuperscript that's part of
% LaTeX
%
% the fragment may be used as a package in its own right, if so
% needed.

I may be wrong but LaTeX used not to have a \textsubscript analogous to standard \textsuperscript. But now the following document compiles under pdftex from TeX Live 2016: 

\documentclass{article}
\begin{document}
x\textsubscript{1}
\end{document}

However, upon compilation, the log file doesn't mention the subscript package. Nor does pdftex complain if \usepackage{subscript}, but, strangely enough, it does complain if \newcommand\textsubscript[1]{}. What is going on here? Has \textsubscript become a standard LaTeX command? Can I just stop requesting subscript from now on?

Best Answer

The \textsubscript command was for many years part of fixltx2e: code which the team felt should be in the kernel but for various reasons did not want to add. At the start of 2015, there was a policy change and the contents of fixltx2e were 'folded' into the kernel. (There is a mechanism to back this out if required.) As a result, any recent LaTeX provides \textsubscript.

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