Not post-specific, rather general policy, but I will use two posts as an example:
A recent question asked: What is this aircraft that has flown over my house all day?
To which I voted duplicate for: Is this a C-17 (and why is it here)? And the asker agreed hence the "Community ♦" vote.
I voted based on both posts (photos) having similar angles to the same plane (a C-17).
But a comment said:
I disagree that this question is a duplicate. One cannot search based on just an image on SE, you can only search text. Given that a person asking to identify an aircraft inherently does not know the name of the aircraft, how can they be expected to find a previous post asking about a C-17?
To which I replied:
And that is why humans are involved, and not a search robot (note that OP agreed it solved their question). The other extreme is having 10 distinct questions for the same aircraft-identification, say a 747 – does not make it right.
So far there are two views, please discuss and vote below (using answers please, so they can be voted both ways).
From personal experience, although I'm not sure if policy driven, duplicate voting based on photos alone is allowed on EarthScience.SE. And I'd imagine the same for species-identification on Biology.SE. (This comment is to highlight that it would not affect only Aviation.SE, so perhaps we can draw from wider-site consensus.)