I'm genuinely confused about why this could be considered a good idea?
I'm genuinely confused why it wouldn't. Too many arguments in programming deal with bikeshedding like camel case vs underscores. Why not eliminate the debate by agreeing it doesn't matter one bit?
It makes Ctrl-f and static analysis a bit harder!
Nim comes with a search tool, nimgrep, that understands Nim identifiers.
You are not supposed to mix different styles within the same project.