How do I develop the habit of consistently reading and commenting on people's content?

You've just answered yourself.

You develop the habit of consistently reading and commenting on people's content.

How do you do it? By consistently reading and commenting on other people's posts.

Impose some targets on yourself. Let's say: Read 10 posts (or watch/listen to the video, if it's a vlog), upvote and comment on at least 5 of them. Daily!

This is one of those tasks you get better at while doing it, just like posting.

Choose and join a tribe or community built around a theme you prefer, so you will easily find content that you'll enjoy reading/watching.