It's likely that FB uses user response to posts to decide how to prioritize them. However, several patents describe systems where they analyze (using CV) and make decision on the importance of pictures before they are published.
Unless your don't want to, but you are obliged to use IG because your business focuses on a demographic on which IG has a monopoly (the 15-25 demographics in the EU).
Of course it is. I'd even say that what we found is probably similar to the issue of offensive suggestions by search engines. A minority of Instagram users see the platform as a free source of soft porn images and their behavior is probably picked up by ML systems, amplified, and pictures of nudity are pushed for all users, in a vicious cycle. Just like search engines spread far-right conspiracies by suggesting them to millions of users after a few thousands searched for them.
Look at the data file, which is linked to in the article and contains the suggestions. It's very unlikely that at least some of them are automatically generated from content found on the web.