I think the deeper point is not about the highlighting, but the ability to interact with the code semantically. If your editor was completely aware of the semantic structure of your code, it could provide very powerful refactorings that respected line-associated comments and things like that.
For example, it you would type a string, and wouldn't need to worry about whether it is represented as multi-line string or not or how to properly escape newlines and special characters. Your editor would know that you are typing a string and do the appropriate thing.
That said, many advanced IDEs do have very sophisticated syntax parsers which can do many of these things already. Light Table and Lisps evolve this even further. I would imagine that a language designed with this use case in mind would enable even tighter integration with the development environment though.
For example, it you would type a string, and wouldn't need to worry about whether it is represented as multi-line string or not or how to properly escape newlines and special characters. Your editor would know that you are typing a string and do the appropriate thing.
That said, many advanced IDEs do have very sophisticated syntax parsers which can do many of these things already. Light Table and Lisps evolve this even further. I would imagine that a language designed with this use case in mind would enable even tighter integration with the development environment though.