It sounds awesome. Unfortunately, it also sounds very tied to a particular dialect of a particular language. For K&R C or then ANSI C (heck, it's not hard to make one tool understand either, as the syntax isn't that different) you get a good return, because there's a lot of code out there and the structure is somewhat regular. It'd be even better for Lisp and most of its descendants.

However, the strength of line-based source control is the same as the weakness you point out: its very generic method. A line-based patching revision control system is more efficient than storing a whole new version of every file with every change, and does not require the up-front investment of a language-aware revision system.

People should, of course, not pass on maintaining comments and code because of the source control. They should, though, avoid making arbitrary changes against the style of the project.