I like it! I don't think it'll break anything; can you send a pull request? Then we'll be able to run such code reliably at the repl! That would be sweet.
Edit 38 minutes later: hmm, there's one issue. Right now you can type multiple expressions in on a single line, but this change would drop everything after the end of the first expression. A better approach would be to drop only whitespace and stop at the very first non-whitespace character.
Yes, my impression is that "stack-based lisp" describes http://factorcode.org to a 't'. In Factor you can throw code on the stack by a process called.. quoting. And then invoke it inside some other higher-order function.
I found this most salient:
"This is totally subjective, but I think we're at a point where the language ecosystem is much more important than the actual language. This was probably not the case when pg was writing software for Viaweb and there wasn't nearly as much FOSS that you could just use. At that point in time the LANGUAGE was probably much more important because there was not a lot of differentiation beyond that. Now, we're at a point where the language isn't as important and the ECOSYSTEM around it is much more powerful that then language itself."