Here are 2 PRs by me:
https://github.com/minetest/minetest/pull/5519 "Sneak: Add option for old move code"
Temporary option for classic sneak behaviour.
Enabled by setting the added 'new move' physics override to false.
By default 'new move' is true.
A temporary setting to enable unchanged old move code while we continue to improve the new move code.
https://github.com/minetest/minetest/pull/5527 "Sneak glitch: Detect ledge for 2-node climb-up"
Re-creates the old sneak-jump behaviour in new code.
Enabled by the 'sneak glitch' physics override.
When a ledge is detected the jump speed modifier is set to the larger
of 'physics override jump' and 1.3 to allow a 2-node climb-up.
An unexpected side-effect is the simple sneak ladder working smoothly.