Define dehorn. Any metal removed from the hammer will reduce mass. All else being equal,, less mass = faster hammer speed = less lock time & better ignition.

There can be tradeoffs. Sometimes it's necessary to use a more sensitive primer, but for me that has usually been associated with using a lighter hammer spring as well. There are some guys out there that radically lighten the hammer, and those guns almost always require some tuning, but for a simple hammer spur bob you could very well be fine. If you go ahead and cut it, you might possible may want to consider one of the Wolff Extra-Power hammer springs if you feel ignition has been compromised. On the older guns it didn't seem to be a major issue, but I've seen some MIM hammers that appear to be partially skeletonized (lightened) from the factory, and that's why I'm sort of waffling a bit here. Extra length firing pins are also available for tuning purposes.

Cutting away metal means less mass.
Less mass means less momentum
Less momentum means less impact to the primer.
I think some have found that they can remove too much hammer and have have caused faulty ignition.

I know on a Super Redhawk I had, I wanted a better trigger pull and opted for lower weight hammer spring.
That worked fine all summer until colder weather. First cold day on the range and I started having misfires. I don't know what made me do it, but I replaced the "weak" Hammer spring and my ignition problems were solved.
Hammer spring just too weak?
Lube that stiffened just enough in cold weather?
Some combo?
Same result . . . Misfires