I don't think Coconut milk is intended as a replacement for regular/soy milk though. Its even packaged in tin cans, so I'm assuming the primary usage is as an ingredient in Southeast Asian foods (esp. Thai Curries)
I think the commenter you're replying to is referring to a type of drink that's a milk-substitute containing coconuts, not the canned stuff that's got tons of coconut oil (and thus very fatty) ... though I love both, it's kind of confusing that their names are very similar.