Ah, finally managed to find the post I was looking for for the links about how fence foundation stacking is or isn’t an exploit.
Funcom did make it clear in the original response that the rules could change in the future (as is perfectly reasonable), but that isn’t really the issue. As can be seen in the second response, it sounds a lot like use of the building technique is considered to be the problem. Or at least I wouldn’t want to stake my build on it (if I was ever on an official server…). It’s not so much the change itself that is the issue, but rather that a rule which appears this stringent could be reversed after so long and yet require digging on the forums to even find out about. That’s what leads to the worries that something along those lines could potentially happen again (and by worries, I mean idle musings…).