The Tavern

In 0.19.0, I came down stairs and met a room full of monsters, including a manticore which hit me with barbs. I was able to go back upstairs without a prompt to confirm movement and without taking any damage. I stairdanced the whole mob away, while barbed, without taking any damage from the barbs! This ought not be, since one certainly must move to take stairs. Being able to stairdance while barbed is a very bad loophole since that is one of the most effective movements one can take.

Nonsense. Stairs are obviously reusable portals that require you to read something off the portal inscription. You are helpless for a few seconds on the receiving end until you are entirely phased-in with the rest of reality, and if you are confused, you might fail to read the inscription correctly.

HEAD-CANON FUCK YEAH

Yeah, stairs never made sense in swamp/shoals anyway...

I don't think the example in the OP means much, unless the little bit of damage from moving once with barbs would be enough to have made you die, since once you've killed the stuff on top, you could just wait a few turns to take the barbs out, then go back down. (and yes, Shoals only makes any sense if you assume its stairs are actually portals)

I just want to know why barbs hurt you even when you're flying.

Head-canon: While flying magically, you have to flap your arms like imaginary wings to move between spaces.

I don't think "You walk upstairs. You die..." is very fun, so while the current approach is a bit of a plot hole, it's better gameplay.

I don't see any difference with taking a step in some direction and dying.

Do we really want to make manticores even more annoying?

Shoals already has a stairs denying monster though. Not that barbs would actually deny you taking the stairs, just hurt a bit...