That is what I thought.
I’ve been thinking about this and would like to elaborate a little on my initial response. A critique has two potential factors, one is hard rules and the other is personal opinion. It is one thing to correct someone when the give wrong information. E.g., crit 1 posts incorrect information and crit 2 brings up the correction in a respectful manner. To me, that is ok.
When I say keep the crit focused to the OP, I am referring to personal opinion. Everyone reads a piece differently. Not everyone will like, not everyone will "get" it. Take your example. There is no reason for crit 2 to invalidate crit 1's personal opinion. It is up to the OP to decide whether or not the crit has feedback they can use.
Now if your example read:
Crit 1: "I thought the ending was weak; it was an anti-climax."
Crit 2: "I didn't get that. I thought it was delightful irony. Would you mind elaborating on what you saw as anti-climatic?"
(Ok, not the greatest rewrite of your example, but hopefully you get the idea.)
In this example crit 2 is not invalidating crit 1's opinion. This opens it up for discussion in which the OP will get useful information. The other option should be to just state your opinion. There is no reason to tell the person that they don't get it, that they are wrong, or that they missed a point. It doesn't help the OP, or anyone else, which is the reason we crit, right?