This happens on my commuter bike with the loose-bearing headset, doesn't happen on the road bike with the sealed-bearing Chris King headset. It's not likely a big deal, but my manual says it IS important when wiping that dirt away to take care to not to push the contaminated grease back into/towards the headset/bearings. Unless your headset has seen a lot of water, or feels rough, I doubt it's anything to worry about.
Sit bones = ~135 mm, saddles that work ~ 155cm/6.1 in wide
2003 da Vinci (custom road/all-rounder)/Terry Butterfly Ti
1994 Gary Fisher Nirvana (vintage MTB/commuter)/Terry Butterfly Chromoly
1991 Terry Symmetry (NOS frame/fork, project in progress)
1973 Raleigh Super Course (project in progress)