From what I understand of policy, this is the general rule:
(note that I may be out of date or simply incorrect)
That's my impression too.
I think a skyladder can be defined as "any ladder that has no part touching the ground or a structure". Even if it's 99% hanging in the air it's okay as long as that last 1% is touching something solid on the map.
During one of those sieges I threw a ladder from one tower to another and rather than fall flat as I intended, the far side stopped about 4 meters in the air above where it should have landed and hung there, incidentally making it an ideal way to reach the far tower without any chance for the defenders to break the ladder from there. Some called it a sky ladder but by
my PhantomZero's definition, it was legal -- it was anchored to the structure. Not my fault the engine decided to stop the far end 4 meters in the air!
The admins didn't say anything but some over-enthusiastic Judge Dredd types broke it anyway. :-p