Adding the line \emph{sty} to the answer in Accessing Junicode ligatures produces a fatal error.
\documentclass{article}
\usepackage{fontspec}
\usepackage{filecontents}
\begin{filecontents*}{junicode.fea}
languagesystem DFLT dflt;
languagesystem latn dflt;
feature liga {
sub t y by t_y;
} liga;
\end{filecontents*}
\setmainfont[FeatureFile={junicode.fea}]{junicode}
\begin{document}
fifty
nifty
activity
\emph{sty}
\end{document}
The problem seems to be that the glyph t_y does not exist in the italic part of the font. What to do?
\? it seems to work without that too. – Toothrot Mar 31 '16 at 01:14