Overheard's emotion feature is unclear

It turns out that the emotion applies not to your reply to the post you "overheard", but to the overheard post yourself. How was I to know this? I thought I was happy to clear up a bit of confusion for a user, and also I can't tell what state they'd list themselves as in (other than, perhaps, happy or angry).
 
sad I’m frustrated
Inappropriate?
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