If you can remove lines of code and retain functionality, then yes, I will pay you to remove code.

Conversely, adding lines of code but NOT adding functionality isn't worth a cent.

Depends if it adds anything else - readability, maintainability, flexibility, portability etc.

The "code as liability" argument seems, unless I'm mistaken, to be based on the idea that less code for the same level of functionality means less cruft, and therefore better support for the NFRs that I mentioned above.

That's often true, but not always.

If you're including those NFRs in what you mean by same functionality, then the number of lines of code is utterly irrelevant.

Arguably, programming class teachers charge students indirectly for adding lines of code without adding valuable[1] functionality.

The market value for code without valuable functionality is negative.

[1] Value as determined by how much anyone is willing to pay to use the software.

Tests and comments.

Comments are useful, if they provide insight. They are not useful, if they do not.

Tests can provide a number of things: they can serve as API examples, assure functionality, speed up implementing new functionality and debugging.

If you tests don't do these things, they are not worth keeping, either.

removing the tree without maintaining the functionality is damaging the asset