u/ZirePhiinix
In addition to Hazzy's comment:
Inertia dampeners off =/= plane-like controls.We have no aerofoil simulation (for performance and space reasons), meaning you won't continue moving "forward" (towards the nose of your ship/spacecraft) if you bost forward while inertia dampeners are off.
What happens is your ship will no longer counter your inertia to try and keep you stable / in place when you aren't providing input.Disabling inertia dampeners is useful when in combat or travelling farther, as you won't have to worry about boost energy while keeping your speed up.
Hope this helps clarify any misunderstanding, here or anywhere else in the future. :)