The first wall of text, as a guy who had Sen's fortress BPed for about 6 hours total, it was set to nit be plagued by other players, and my SL was high enough to allow no interruption. However they disappear after a while... It just takes time and interaction of things. Their is no real solid cause of removing such Perma-Gravelording... That technique is what me and Fear used constantly.
For the second wall, that is indeed informative in relation to Gravelords and Infestation. It is clear that the Gravelord Sign is not entirely connected to the BP infestation well... This shows a good example as of disconnection... I wonder if BPs can cycle from one world to another and infect different three people randomly. I wonder if the Gravelord that the guy/gal was testing with was invaded, or was attempted to be invaded (as we know that Gravelords usually have a hard time in terms of connection).
It's good comrade. I recommend that you get more information. If you have any questions, I'll give as much information as possible about the Great Nito's greatest use of Disparity. Just ask away, and I'll try to answe as best as I can.