To help further the discussion in this thread, and trying to do it in the least aggressive manner possible, the very first time that I ever noticed something 'going on' underground was in Brindleton Bay after C&D was released. I immediately cleared the 64x64 lot, hoping to build a something spectacular on it, and of course doing my usual of cutting out the under-ground only to then start building up on it, but instead of having a clean, open sub level, the water from the ocean/bay next to the lot was what I saw filling the open space after clearing the top ground level. IIRC, that has since been fixed (if silently), and it was right around then IIRC that they released the first-person camera mod that they basically said was 'modded-in' by someone in-house from the dev team. To add just a bit of salt, the whole extra two sub-levels that came out shortly thereafter acted (to me, from my original bug report) to have been 'modded-in' as well, in that there were too many issues that I was experiencing (verified by BryonyRae) with being able to not only add paint to the inner walls of a sub-three or four (sometimes even sub-2) floor, or being able to alter any walls without experiencing the 'dirt flooring issue' that we now have as a permanent fixture (until it gets solved). We who use & know this method of building are seemingly few, but for us who do use it a lot and enjoy it, it is a nightmare to have...
