This article really makes me want to learn lisp. Is there a risk that lisp’s extensibility creates lots of very specific dialects of lisp that can be difficult to share / understand?
On the other end of the spectrum, Racket[0] fully embraces the DSL-creating power of macros.
To answer your question: I think that lisp's extensibility can be used to create something difficult to share/understand OR easier to share/understand [1]. Whereas some other languages might be limited by their ability to naturally express a domain-fitted solution, yet they make it easier to avoid creating a cryptic mess. So... lisps don't confuse people, people do.
[0] - https://racket-lang.org/
[1] - a good example of macro use is Compojure's use of a macro for http route definitions. https://github.com/weavejester/compojure#usage
I went from Common Lisp to Chicken Scheme to eLisp and found the transitions very painless.
I've also peeked at code in various other Lisp dialects, and they've always been very readable to me.
If you're asking instead about DSLs written in Lisp, then the relationship of those DSLs themselves to Lisp is up to the author of the DSL in question. They can make the DSL very similar to Lisp or very different. It's entirely up to them.
Most of the Lisp code I've seen has stuck pretty close to Lisp itself, which makes it easy to read for anyone who knows Lisp.
Reach out if you end up having any questions!
As to the risk of specific dialects being too difficult to understand: this isn’t the case in practice. There’s a few of reasons for this, but the main one is that, you can’t deviate from lisp’s simple syntax too much — as soon as you do, it’s no longer a lisp, and can’t use macros in the same way