Oh, I see what you're saying. I missed the @ in your reply and thought you were referring to to npub in general. Yeah, that's kinda weird. @npub is supported on pretty much every client I've used other than 0xChat. Perhaps they'll add it in a future relase?
Discussion
the thing, some clients are using it, others are not. so interoperability was compromised by clients implementing non standard features.
It's always frustrating when a client decides to buck the standards in favor of some unique implementation. I wish interoperability was prioritized more often than it is.