The following example produces different results when processed
by LMTX and MkIV. In particular, a space between the X and Y is
not auto-inserted by LMTX, while it is by MkIV.
\starttexdefinition TEST #1The MkIV result is the correct result (in my opinion).
#1\autoinsertnextspace
\stoptexdefinition
\tt
\starttext
\TEST{X} \emph{Y}
\stoptext
--
Rik