I wonder to what extent this is a function of how one uses Instagram: ie, perhaps the parent comment's feed contains posts superficially similar to ads, while the composition of yours makes ads stand out in content and caption (my experience is closer to yours on Twitter and upon occasionally IG use).

Tangentially, I find IG's place in the social media panoply to be fascinating. It's the only service that everyone seems to feel positively about: it doesn't inspire the loathing that Facebook and Twitter does or the mockery that Snapchat does (even by their users).

But watching people use Instagram is the closest I see people coming to the popular addict/junkie metaphor and the stereotype of smartphones and social media turning us into slackjawed automatons in thrall to a colorful Skinner Box. It's really eerie.