I last saw this trick about three years ago, when I got some absolutely horrid Chinese boots: to watch the movie without Chinese subs, you were actually watching the hard-coded Chinese subs with DVD soft-sub black patches added!
By the way, if you're opening stuff in VDub, then whatever you do there will have to be re-encoded. VDub does not edit MPEG-2.
In fact, if you're using VDub anyway, what are you doing messing around with DeLogo and the like?? Just lop off the black bars that are there, and add them in again. In AviSynth, that takes exactly two commands, Trim() and AddBorders().