The ambiguity I was addressing was grammatical, not biological. "now significant" could be a typo for "known significant", "non-significant", "no significant",

The ambiguity I was addressing was grammatical, not biological. "now significant" could be a typo for "known significant", "non-significant", "no significant", "not significant", and possibly others, including not being a typo at all. Likewise "significant" itself could mean different things in this context. E.g. phenotype neutral mutations can be highly informative when tracing origins, mutations in "non-coding" regions can have huge regulatory effects, etc. I agree that your interpretation of the post to which I responded is plausible, but it's not the only one.