Is compatibility with older hardware decoding at all important for you? I believe what Ben meant was that the benefit from going 10 bit with x265 is very small (unlike x264) and because bluray is only 8 bit there is no good reason to use 10 bit.
Edit: the mention of not visually lossless at lower bit rates simply means re-encoding does hurt visual quality, unless so large it is pointless. 10 bit or 8 bit.
My understanding is that 10 bit is never worse with x265, perhaps slower but not lower quality/size. However, unless you resized or did some filtering at a higher bit depth there is not really a benefit either. I still use 10 bit when I don't care about broader hardware compatibility (usually) but I do not notice a real improvement whenever I have casually tested it. I think memories of x264 are too strong and are twisting Internet advice (and my behavior).
The situation is mildly depressing because x264 gets a big benefit when encoding 8 bit content as 10 bit but almost no hardware decoders can handle it, while x265 does not benefit much if at all from encoding 8 bit content as 10 bit but pretty much all new hardware decoders can handle it.
