...see the version of the file here, where I corrected the errors in the MML: http://simplici7y.com/items/marathon-red-addenda-fixed
I also removed the red fog, since fog was not a feature of Infinity and thus RED did not have it.
I don't know if these are available elsewhere nowadays, but the copy available at "http://files3.bungie.org/trilogy/MarathonRED.zip" has incomplete mml.
So, here are some mml tags to make your copy more like the original Marathon RED. A few things are changed slightly; those are marked with a <!-- --> tag.
Enjoy.