Reddit not long ago announced a plan to delete all comments from a submission whenever an OP deleted their submission (ordinarily only the OP's post would be deleted).

There was quite a lot of pushback since the consensus was many comments aren't just for the benefit of the OP but everyone (in fact sometimes the OP doesn't even appreciate the comments they receive but are nevertheless useful to others).

So Reddit walked it back but it does show many of the site's users are conscious of the broader utility of comments outside of just the smaller contextual interactions.