I've tried context --ctx=s-mod with some files, e.g. t-annotation and I only get corrupted PDF files. Also, when I try with files such as syst-aux.mkiv, I get the following error after a L O T of warnings:

\wait

tex error       > tex error on line 4554 in file syst-aux.mkiv: ?

<read *>

\wait ->\begingroup \read 16 to \wait
                                \endgroup
\installsystemnamespace ...??#1\endcsname \writestatus \m!system {duplicate system namespace '#1'}\wait
                                                                                \else \global \advance \c_syst_helpers_n_of_names...
l.4554 \installsystemnamespace{extraevery}
                                   

<empty file>