I stand corrected.
> I'm not sure there are such formats these days.
> mex still exists.
> cs(la)tex still exists.
I don't know about mex (what is that?) but is cs(la)tex doing anything other
than hyphenation support and font stuff?
> Not saying they are completely independent of latex (they aren't), but
> they do exist as separate formats.
actually you are right they provided some hacking into input encoding support
in case of cslatex if I remember correctly (but then perhaps I don't) but most
if not all of that should be doable via a package rather than via a
format. Hpyhenation is a different story though.
> But even if, the question remains what you gain.
:-) but perhaps there are