if(condition) {#block never used} else {#actually do a thing}

Vs

ifn't(condition) {#actually do a thing}

Vs

if!(condition) {#actually do a thing}

Cannot start a statement with else. One can with ifn't. There is a new thing where we don't branch (which is a separate discussion).

Or am I missing the joke...

I personally have a gut feeling of rejection for every language having the unless keyword. This is why I hardly know any PERL and Ruby for example.

I have mixed feelings towards Kotlin's takeUnless scope function (I nearly always use takeIf with a negated predicate) because my mind forgets the unless version exists.