Maybe? I guess I'm speaking from personal experience here when I say writing in-depth sourced and edited comments[higher quality] is more difficult for me on a mobile device. But perhaps, my experience not the norm. Is it different for others?
The proportion of users on mobile devices could explain some of the sliding quality. I know if I am using a mobile device, it's primarily for content consumption. I can't quickly reply in any depth with a mobile keyboard, so that waits until I am at a full PC, which is a smaller and smaller proportion of the time I am actually using Reddit in recent years.
Engagement isn't about how much time you spend in the editor writing insightful comments. It's how much you scroll through the feed laced with ads. Sadly.
