The first good implementation I'm aware of is Egil Möller's from 2003 (https://srfi.schemers.org/srfi-49/srfi-49.html). My independently researched prediction in 2017 was that no one will ever discover a place where parens or other visible syntax is needed. That sets up an easy proof by contradiction (and I've built a database of over 10k languages so far, looking for a single scenario where you would need them, and haven't found one yet). Here are 19 demo languages covering lots of scenarios demonstrating utility without parens (https://github.com/treenotation/jtree/tree/master/langs). A glaring hole though, now that I think about it, is that I don't have a good Lisp-like Tree Language. I think a Bel Tree Language would be an excellent example project (and I'm happy to assist anyone who wants to make an attempt, and if no one has the bandwidth and it's not done by next year perhaps I'll find the time to give it a go).

> They are the structure that supports Lisp's simplicity and consistency, which is what all the good things come from.

I agree with this, but would say they are "one" structure, not "the", and that there are other options (I have one idea in tree notation, but not ruling out that there are more, perhaps better ones).

> If you take them out, it gets complicated and isn't worth it.

I agree with this, but think there is a future tipping point related to tooling. Tree Notation was quite terrible 2 years ago, but now with type checking, syntax highlighting, autocomplete, I hate to use Lisp and other languages (everything feels unfinished, because I know the syntax characters can be removed).

I think we'll hit a tipping point where the tooling for Lisp without parens is good enough that the benefits of dropping them make dropping them a no-brainer. Could I be wrong? Sure, it's a forecast/prediction. But I want to encourage people to invent new alternatives, to try everything under the sun, and not to settle that they are somehow needed. We can make it better.