We used to dump fuel (JP5) regularly in preparation for landing aboard ship. Sometimes you would fly through the formation lead's plume (emanating from the wing fold area). We tried to keep the intakes out of the plume of course, but more than once I had my windscreen washed
. Never had problems. Never heard of any but not saying there were none.
Having said that, I can faintly remember an airline accident involving fuel dumping probably in the late 1950's off the east coast of the US.
Wouldn't be surprised if some of these restrictions on dumping/jettison of fuel date from the piston engine era.