Marinating Eggs in the Shell
Has anyone ever done this? It seems like it should be possible since eggshells are porous. On the other hand I've only heard of this being done in limited applications (like tea eggs). Given how widely used eggs are I would expect there to be many more similar recipes, but I'm coming up empty.
Anyone have recipes/reasons why there aren't more recipes?
Yes, all the time.
It's how Chinese salted duck eggs are made. The raw eggs are soaked in salt brine for about 30-40 days before they are boiled and either eaten as is (in rice or congee) or made part of Tsong-Zi or Mooncakes.
There's also Chinese "Thousand Year Old Eggs" which are made by preserving duck, chicken or quail eggs in a mixture of clay, ash, salt, quicklime, and rice hulls for several weeks to several months, depending on the method of processing.