It's a UK variant of Murphy's Law - "anything that can go wrong will go wrong". The "sod" part is because anyone affected by it can be said to be an "unlucky sod" - here, "sod" is used to describe somebody who is particularly put-upon, rather than an expletive or insult.
With this in mind, Relayer's usage of it doesn't make sense in that context - Deano simply came across the phrase we'd been discussing in the novel he's reading, which is either a coincidence or Alanis-style irony.![]()
Yeah, more of a coincidence than a disaster I suppose, but it did seem odd that after posting unfamiliarity with the phrase he came across it so soon.