For my main Italy collection all mint stamps are mounted in Hawid mounts
with black backing, even if mounted already.
I have one quite expensive stamp that has once been mounted, with an attempt
to remove the mount leaving
what was described as gum disturbance, which is fairly major. Frankly it
would have been better to
leave the hinge on, as I will only ever display the front of the stamp:

http://www.italianstamps.co.uk/kingdom/airmail/sa25.jpg

As you will see, the front is unaffected, and I like the fact that this
stamp is not only marginal but
has the sheet serial number on the selvedge.

If the stamp has a hinge that has so badly affected a stamp that its remains
are visible from the front,
then find another specimen! Removing the hinge probably will not improve
matters.

Depending on the nature of the gum used, gentle painting of the hinge with
tepid water may well
loosen it enough to remove it without excessive gum disturbance. I would
not do this with an expensive stamp!

--
Tony Clayton