I noticed reactions were available in the sell section (however briefly) and aren't anymore, and are still available in the buy section. I don't really mind but i don't think they serve much of a purpose there.
Where they would have a purpose imo is the price check section. people might agree or disagree with a pc but arent inclined enough to post themselves. reactions would be an easier and quicker way for that and an additional indicator for the person who asked.