and that some people were doing this on purpose, and then linking to the wayback copy instead 'just in case' the original came down or was edited.

Ewww, no! That's awful!

But I tend to assume if it's a public DW post it's okay to link, unless stated otherwise in the post.

Yeah, I'm usually that way, but I will sometimes ask for things that are personal or potentially controversial. People might not realise that the thing they're saying is link-worthy, and a heads up seems kind?