I had a bad(?) experience with Mercari recently.
I bought a pair of speakers, but the seller neglected to include the copper-coloured audio cable so there was no way for me actually hook them up and test them.
Of course I could have just bought some speaker cable, but I don't want to do that just to test if something works, especially when it was included in the product listing.
I contacted the seller and they told me to check the box again and of course I told them that it wasn't there.
No reply, so I decided to wait a few days and give them a chance to respond.
Still nothing, contacted Mercari support and they told me to contact the seller again and wait 24 hours, after which they'll take over.
No response, Mercari escalated the matter and contacted the seller directly giving them 24 hours to respond.
The 24th hour passed a moment ago, so Mercari support automatically cancelled the transaction, and refunded me the money.
So now I have money in the bank and an expensive pair of speakers.
Everything worked out in my favour but I'm not really sure how I feel about the whole thing.