tl;dr: I don't really know. I was probably wrong. I am sorry.
I have been the evil guy that declined this flag.
I find it very hard to distinguish between what is a low quality answer, what is not an answer, what is a mixture of both. Most of the times those flags are very helpful and easy to cope with. Sometimes you end up clicking the wrong button - it happens.
Sometimes there is disagreement within the community. It then comes back to the mods, who have to sort it out. And since we are all human we might make faulty choices.
I did not want to be content police in this case, because I saw the intention of the post. And while I really thought that this answer had terrible style/formatting and it was based on a wrong premise (that had been pointed out in the comments already), the core principle was correct. (The stabilising effect of the intramolecular hydrogen bond.) This is the main reason why I declined the flag in the first place. (It has now been removed anyway.)
Was the flag helpful? Yes it was. I should not have declined it. I should have probably left an encouraging comment on the post and maybe fixed the language a bit. I apologize for not giving you a helpful on the flag, I will pay more attention next time.
However, let me just run you through the timeline of this post, to point out why such things can happen.
the post was reviewed through the first posts queue, without a comment, which I would think it could have profited very much from. See also: Shouldn't we be a bit more welcoming to new askers/ posters?
the post was reviewed through the late answers queue wit "no action needed" which is very obviously not the case; another opportunity to be welcoming missed
I should have left the flag unattended for at least a day. It might have been cleared from the community this way, or it would have been disputed by the community (it was on this path anyway), putting it back on our table. And then what?
The meta effect (new flag shortly after this meta question) then lead to the deletion of the answer.
All in all, I guess we all learned something from it.