From what I've read, the amount of phosphine plays a role, i.e. if there's lots of it it's a stronger sign of life. However, that's what I've read in the lay press that reports on the opinions of experts. Now, the thing about the opinions of experts is that there are always other experts that hold a completely different opinion and when you read an interview with one expert they very strongly support their own opinion, but don't really do justice to the opinions of others- because that's not their job. So it's often hard to know which expert's opinion is closest to the truth by reading what one team of experts tell the lay press. Science is a debate, after all- but not a debate carried out in news sites and internet forums (or at least not primarily there, I understand theoretical phycisists like their internet flame wars).
So, personally, before accepting anything as evidence of this and that, I'll just wait patiently until the dust has settled and the experts have agreed to disagree.
I wish more people did that when it came to my own area of expertise, btw. What I say above is what I've observed on reportage of my own field in the lay press.
It's a casual dismissal only because it's a comment on HN, rather than e.g. a review comment in a peer-reviewd journal. Otherwise, that's exactly the kind of reaction one learns to expect when one is doing research. Your work will be criticised. Ruthlessly.
It's not even a bad thing, long-term, quite the contrary. Only work that has survived the criticism of experts in a field can be expected to make a real impact.
And this is really just me being philosophical about it because of course criticism stings and rejection hurts. But you learn to live with it and I think most researchers who have taken a baptism of fire (submitted to a journal- or conference in CS) eventually come to terms with it: people will rubbish your work constantly. Until they are convinced it's good work.