I would have raised a fuss about it if it was marked fixme or whatever too, those comments are basically meaningless.  The only valid use I can think of is to leave a note to do something later if you DON'T make a change to it, if you MAKE a change, do it right.

"I'll need to adjust it later" makes no sense, adjust it in veh_type.h.  If it forces a rebuild and that's a significant problem, move vpart_list to an appropriate .cpp file and leave an extern declaration in veh_type.h, there shouldn't be any data defined in .h files anyway.