When I say plaintext, I mean like a .c file--a bag of bytes that may or may not parse into the AST you intend. Modern editors dress plaintext up with syntax highlighting, auto-complete, folding, and such--the code has a veneer of structure--but the basic representation remains plaintext. (And for good reason... plaintext is easy to edit with existing editors, tractable, easy to parse, somewhat easy to tool, moderately easy to version control, and hard but possible to transform automatically. But I believe plaintext is only a local maxima in code representation. We just don't have a good enough editor for code ASTs (yet)).

Now in the Wolfram Language REPL they have some rich input capabilities like http://reference.wolfram.com/language/example/BooleanOperati... . I suspect these are still underpinned by plaintext dumps internally, though, judging by http://reference.wolfram.com/language/tutorial/VariablesInPu... .

I should have said that they've gotten farther than anyone else so far, perhaps, but I haven't tried WL yet, so who knows?