Are there any good/heathly addictions on the internet?
It's subjective but I'm interested in what people come up with. I would say Hacker News is addictive and good for you, but that's debatable...
* Contributing to Wikipedia. (Check out Citation Hunt: https://tools.wmflabs.org/citationhunt/)
* Being an active member of insightful online communities.
* When you encounter an interesting piece of information, archive them with archive.org.
* Reporting harmful content.
I think mostly passive consumption of technology is where it tends to turn more negative if done excessively. I've never seen much good coming out of excessive consumption of sites like youtube, reddit, news media or anything else of that sort.
I don't consider commenting or liking posts on any media platform to be an active participation btw.
Good/healthy? Well... There's almost nothing good or healthy on the internet that doesn't have a not-so-good side. You could go down a new career path by learning on MOOCs websites, like cybrary.it or Coursera.org: you can pick up a whole new skill by watching YouTube videos.
For me, I think the addiction itself is the bane. Not the websites in themselves.