First, something I wasn't necessarily aware, but that probably won't be changed now, using ! to negate a %variable or an identifier inside an if statement works on any token, even on passed parameter:
//alias custi echo -s called custi with $!1- | if (!$false !$false $custi(!$false)) echo -s $v1 -- $v2 | alias custi
Howver, the above will actually fail as a condition, and will trigger the else statement:
if ($true $true $null) / | else echo -s ??
This looks like a bug to me.
Then, //if (a b) echo -a ?? gives a /if invalid format error, but the format seems valid to me, unsure for how long this has been happening, it should also accept this as valid imo, and sets $v1 to "a b".