The issue isn't so much that character(0) is a zero-length vector and "" is a length 1 vector containing the empty string, it's that you can't necessarily rely

The issue isn't so much that character(0) is a zero-length vector and "" is a length 1 vector containing the empty string, it's that you can't necessarily rely on other people's code returning one or the other: things that 'nearly' always return a one element vector (which may contain the empty string for 'nothing') can vary unexpectedly if it fails on an edge case. And, unless you catch it correctly, this can cause downstream failures with little in the way of warning (because a zero-length vector is obviously a 'sensible' thing to return from a function in the usual case). In that sense, it's similar to the problem many languages have with NULL, but on steroids: you can have NULL, NA, character(0) (or anythingelse(0)), or '' as your null result and each of them are tested for in different ways. Obviously this won't be a problem for the various battle-tested standard libraries, but a lot of my work in R at least is assembling somewhat-novel analysis pipelines based on quite new statistics code.