Originally posted by Batman-PrimeClones have fooled abstracts before. I have never seen it mentioned in an ann bio or Thanos bio. It's an obvious joke squeezed in at the end of an issue.
Signifficant issues = canon. In that "signifficant issue" statement from the Watcher that it is the real Thanos and no clone = real Thanos down.It can't become clearer then this.