By using canonical S-expressions, one can even get binary-safety: https://en.wikipedia.org/wiki/Canonical_S-expressions

It's at the cost of human-readability, but it's still readable enough for debugging. Editor plugins could probably fix this issue entirely, by presenting the contents as a more "normal" Lispy syntax.

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I think the Redis protocol is also a pretty good binary-safe-but-otherwise-text interchange format: https://redis.io/topics/protocol

One thing I'd do there, though, is to change CRLF at the end of a line to LF. Well, that and of course also drop support for the legacy protocol, unless one has a good reason to keep it for debugging.

SXML (the scheme tooling around a certain form of s-expression XML) is by far my most favourite way of working with XML.