Colons are a little bit special in Bournish shells, since they're a delimiter in variable assignments after which tilde expansions, and some shells extend this

Colons are a little bit special in Bournish shells, since they're a delimiter in variable assignments after which tilde expansions, and some shells extend this behavior to command line arguments. Frankly, I don't find it outside the realm of possibility that there's some combination of options that will make :memory: misparse on a popular shell, I just don't know of any...