the right ferrite will not "eat up" the signal, but round it some. Thus ferrite protected signals should be fed to a schmitt trigger.
Emphasizing the above, if you are feeding a ferrite protected signal to a regular input you may, very well, make matters worse by using the ferrite. As a rounded signal is in the noise margin critical zone much longer than a square pulse noise can get by so much easier, if no schmitt trigger is used.

Erikj