AST should have one default and one toggled sect

[AnotherPerson]

The problem is that if diurnal is the default, there would be no animation for it. You could have one for activating nocturnal, but deactivating it (to get back to stanceless = diurnal) would probably have no animation.
But we lost so many nice animations already that it doesn't really matter anymore anyway.

You know how Standard Step for DNC turns their other skills into dance skills - but aren't hotkeyable? However Standard Step and Standard Finish both swaps the effect of the Dancer skills.
There can be a skill called 'Sect Stance' that works like [Play] which has a different skill icon, but because Diurnal Sect is the sect trait (like auto-hide for Gatherers), The 'Sect Stance' turns into Nocturnal Sect with Nocturnal Sect animations when added to the hotbar. Similar to how [Play] becomes [Spire/Ewer/Balance/Spear/etc.] whenever a player uses [Draw] and gains the card buff indicating they are holding a card.
When using Nocturnal Sect, the Sect Stance skill turns into the non-hotkeyable 'Diurnal Sect' skill that when used, plays Diurnal Sect animation, disables Nocturnal Sect skill buff, and gives the Diurnal Sect buff, changing the Sect Stance skill into Nocturnal Sect.

It works similar to DNC's Standard Step buff where Standard Finish removes Standard Step - but different in which there's no timer associated with the buff.
So Auto Diurnal Sect (Standard Step) -> Nocturnal Sect (Standard Finish) -> Diurnal Sect (Standard Step)