The rational seems to be making numbers easier to parse for humans, so to me this feel more like a feature in an editor and not the language
Adding such a change to the language makes the syntax for numbers more complex, doubling the work for all tooling to process correctly. So this would affect editors, LSP servers, format tools, linters, etc. So a change not limited to the Clojure reader.
And once added, code bases could easily become a mix of styles, adding to confusion and frustration, requing time for development teams and maintainers to decide which number format to use.
There are already editor features that display lambda functions and partials with fancy symbols.
Many editors also colourise Hex colour codes.
All of which does not require a change to the underlying langues
The benefit of having this as an editor feature is that it could be configurable as to what separator to use, e.g _ , . With comma and dot useful for currency values.
Without changing the underlying language, then the ability so search and use other text tolls remains unaffected.
I would prefer not to include this feature in the language and encourage those that find it useful to reach out to the maintainers of the editing tools they use.