Hi Kristina, I think my main take on this is that source citation is nice, but it doesn't exempt you from copyright laws. If you're in marketing, you must know that getting permission is more important than crediting the source. I didn't get fined for not quoting the source. I got fined for not having a licence (permission), for copyright infringement.

Using a screenshot doesn't exempt you from copyright laws (as far as I know!). I'd be asking permission from the copyright owners if I wanted to use those screenshots. No idea about Quora. Users need permission. Whether or not they need to quote the source depends on the licencing agreement that comes with the photograph purchase and the T&Cs on the platform (Quora/Medium) where it's used.